Category Archives: Street Network Evolution

the evolution of urban street patterns over time

Choosing a grid, or not

In an earlier article we discussed Portland’s grid flaws, prominent among which was inefficiency of land use.

We looked at Portland’s 200’ by 200’ block in the context of other layout options and, when we compared it on a number of criteria, it did not fare well. New data* on other American city grids, that emerged since, which are analysed here, sheds more light on this assessment and also open an opportunity for refined versions.

We argued earlier that if the merits of the specific Portland grid plan were self-evident to planers or developers, its use would have been expanded in the city beyond the original plating of 1846 and imitated by other cities, neither of which has been the case.

For this analysis, we used twenty city grids that range from a mere 150 by 150 feet, just over one half acre, to the ten acres of the largest American grid of Salt Lake City (660 by 660 feet). These gridiron layouts also span a range of street right-of-ways (ROW) from 30 feet to 120 feet.  The present analysis focuses exclusively on comparing land use efficiency among the twenty grids. It consequently raises the inevitable question as to which would be a suitable candidate for a contemporary “town”, “Planned Unit” or a suburban subdivision, if any at all.

Figure 1: Chart showing the influence of the right-of-way width on developable land.

We did two types of calculations: a) we measured the land use efficiency of each one in the set by calculating the ratio of buildable (or saleable) land to the total land that includes the right-of-ways (ROW) for streets, as platted and b) we did the same calculation by adopting a constant ROW for all in order to see the effect of the grid frequency (street frequency or street density).

Chart one finds Portland as the third least efficient of 20 urban grids with a buildable land use ratio of 59% and an implied 41% of land dedicated to ROWs. This finding confirms the earlier assessment. The trend lines in the chart reveal the inverse relationship of ROW width to the efficiency of land use, as might be expected. What emerges as more instructive however, is the amount of difference between a low performing grid (e.g. Houston) and a high one (e.g. Charlottesville). From the 57% of the former to the 75% of the latter there is an approximate 30% jump in land use efficiency. Such difference would impress any urban planner and would be decidedly a priority for a developer. Each for a different reason is keen in optimizing the yield of land put to urban use: sustainability for the former and economic viability for the latter. Interestingly, the Houston city block is 1.3 times larger than Charlottesville’s, yet less efficient; a counterintuitive fact that lead us to look at the influence of block size.

 

Figure 2: A chart showing the correlation of grid block size and land use efficiency

Chart two demonstrates the impact of block size after removing the variability among ROWs and adopting a uniform 60’ width for all cities. Portland now appears as the second least efficient grid in the set, confirming again earlier assessments.  The difference in efficiency between it (59%) and Denver’s (71%) is about 20%, not an insignificant gain in saleable land and reduction in infrastructure costs.  (The exceptional efficiency of Salt Lake City is only apparent as we shall see later.) Instructively, Charlottesville migrated from the most efficient in chart one to the third least efficient (below Houston) in chart two, due to the adjustment of its ROW. This chart reveals a strong correlation between block size and land use efficiency; the smaller the block the lower the efficiency of the grid. Looking at both charts simultaneously, the correlations among all three variables become clearer.

Based on this analysis, we can now consider an optimal, simple, open grid; or perhaps not. There may well be other considerations that would suggest abandoning the homogenous, repetitive grid altogether in favour of another type of layout. Endurance, for example: If replication is any indication of merit, the record does not bode well for the simple grids of the set (as can be seen in Google Earth images): Few of the examples in this set show a continuations beyond the original mile square plan; the majority begin to grow in size, change proportions and even geometry. And as for new towns or subdivisions using them as stencils, the current record is empty. In addition to low survival rate, there are also persistent old and new criticisms.

Key planning figures either through theoretical works or by virtue of built projects have denigrated the simple grid and, in some cases, even orthogonal and rectilinear layouts.

Olmstead in the 1800s abandoned orthogonal planning and introduced curvilinear streets that were to become the model for innumerable subdivisions. Camillo Sitte portrays the grid as unimaginative and unworthy of consideration for new towns. Raymond Unwin in his writings and works rejects the simple, open grid, succeeds in ushering the cul-de-sac through the British parliament and lays out plans free of the rigidity and repetitiveness of the simple grid. Serge Salat tells us that “Unwin joins Sitte in recommending a great variety of street widths, which would enhance the specific character of each street. In the design of districts, the interior streets should not be too wide.  Wide streets planted with trees should be reserved to the outer boulevards where they offer the threefold advantage of serving as promenades, ensuring traffic between districts and delimiting the districts”. In other words uniformity of street width diminishes character and inhibits delineation. In the same vein, Lewis Mumford writes a scathing critique of its use in town planning adding that “..The new gridiron plans were spectacular in their inefficiency and waste”. Clarence Stein creates a model that follows in the footsteps of Unwin dismissing the grid as entirely unsuitable for our times. Recent pioneering projects such as Village Homes, Davis ,CA; Seaside, FL; Kentlands,  Gaithersburg, Maryland;  and Laguna West, Sacramento, CA use layouts that abandon the simple gridiron pattern.

Figure 3. A sampling of 3 simple grids and their corresponding percentage of land used for ROWs.

From the very recent perspective of seeing cities as organisms that obey fractal laws (seen in the works of Alexander, Salingaros, Mehaffy, Mashall and Salat), more fundamental weaknesses of the uniform grid emerged. For example we read that: “Making a line straight, or regularizing a street, as 19th century urbanism has often done, eliminated intermediary scales and hence the possibility of geometric interaction and coupling of smaller scales. In other words it killed life. For thousands of years, historical cities avoided straight lines, creating multiply connected rich structures by way of slight discontinuities in relation to straight lines.”(Salat)

The same author infers that the intent that drove the creation of the simple grid may not have been entirely benevolent: “It is only when an absolute power absolutely controls the ownership and use of the ground that the city can conform to a perfectly geometric form, as was the case in the ancient Chinese capitals or the cities of colonial occupation in North and South America”

In the last 20 years, researchers confirmed the heightened risk of collisions that grid layouts engender and the negative role its unfiltered permeability plays in maintaining security and sociability in a neighbourhood.  Also, from a sustainability perspective, the grid plan has been found deficient because of its potential high ratio of paved surfaces; its land waste; its disruption of natural land features and its low operating traffic speeds.

In spite of this evidence against the simple grid and the complete absence of new applications of it, we may still wonder if a simple grid can be chosen on the basis of two known grounds: its legibility and the speed at which it can be surveyed. All simple grids in the set share these attributes irrespective of their size.

Figure 4: The turning radius of a team of four oxen pulling a four-wheel cart determined the width of the streets in Salt Lake City. (Image source: Wikipedia)

Knowing the relative impact of the variables we examined, the choice among grids becomes easier but, heeding the criticisms, also irrelevant. However, an opportunity opens up to manipulate them by selecting desirable elements from each; no need to copy uncritically. For example, the highly unusual, 120-foot ROW of Salt Lake City’s streets (based on the long-outdated need for a team of four oxen pulling a cart to turn around within the street) would be unjustifiably wasteful and unpleasant if used for residential streets, where traffic is low and buildings small. Similarly, its 660 by 660 (10 acre) block size (based on homesteading family units, mostly extinct now) cannot be subdivided efficiently for current two-income-earner family houses. These historic changes in socio-economic structures are in fact reflected on the ground; many of Salt Lake City’s original blocks have been divided in half by a mid-block road. Consequently, its exceptional theoretical efficiency on the chart evaporates in practice and renders the block as found unusable. Clearly, choices should be made with an eye to current socio-cultural conditions.

 Modifying the ROW width can definitely lead to substantial efficiencies, as we saw. Charlottesville shows the way with the narrowest streets in the set (30’ and 40’) and highest land use efficiency (chart 1). But we need not copy Charlottesville. We know many Greek, Roman, medieval and Arab streets to be much narrower, starting at 6 feet and averaging around 15 feet wide. All these streets functioned adequately for pedestrian movement and still do in surviving city centres that date back to original layouts. But, as with the block sizes, current trade, work and transportation modes bear little resemblance to those when these streets were conceived and used; direct copying may not work.

Figure 5: A 6-foot (left) and 12-foot wide streets (right), millennia old, worked well for the foot-and-hoof traffic of their time.

It is plausible that earlier street dimensions might find an application in contemporary networks: Salt Lake City’s 120 width, for example, as a divided boulevard with six lanes of traffic and a 30-foot linear park for pedestrian movement on either side while a 15’-wide Roman street, as a pedestrian-only, landscaped route connecting wider residential streets that are designed for car access. In this vein, efficiency can be matched with purpose.

Figure 6: Savannah’s composite, 13-acre cellular grid, at 55%, and a 40-acre, contemporary cellular grid at 74% land use efficiency. (Plans at same scale)

Breaking the convenient, but unnecessary, uniformity of the 18th and 19th Century American grids would be a first step in recovering the land efficiency mandated by current ecological and economic imperatives. Pointing in that direction, Savannah’s composite, cellular grid includes variable size streets and blocks for private, civic and religious functions. A second step would be to include block sizes that can accommodate comfortably prevalent building types and sizes unknown in the 1800s, again defying block uniformity. A third step would be to adapt its streets for the now universal motorized mobility, of cars, buses, trucks, trams and motorcycles, that is radically different from when oxen, equine and legs shared the transport of goods and people.

In summary, examining the simple grids in this set serves as an introduction to optimizing land use, people circulation and the movement of goods. The resulting challenge is to use these insights to develop patterns that accommodate contemporary urban land economics, transportation, environmental priorities and citizen aspirations as these patterns may have done in their time.

Fanis Grammenos, Director
Urban Pattern Associates

*Credit goes to Daniel Nairn (http://discoveringurbanism.blogspot.com/) for the list of American grids with dimensions.

This article was first published in Planetizen.com

 

Can Money Grow on Trees?

When calculating the cost-effectiveness of any operation economists talk about externalities. Mostly they mean the costs or damages to others either downstream or in the future that are excluded from a calculation.

But are externalities always a cost?   Could they be benefits, unforeseen profits and, if so, how would we know?

To know confidently, we need to do more arithmetic than fits on the back of a cigarette package. Incidentally, that package is a perfect case of an externality, when a nearby smoker inadvertently loads my health bill; he only pays for the costs of cigarette production. Or take the case of the new glass tower whose reflected sunlight caused an overload on the cooling systems of an adjacent building. Could someone have calculated in advance the effect and cost of the additional cooling capacity?  

On the other hand, we can assume, speculatively, that the entire building surface had a special selective coating that absorbed 80% of sunlight and turned it to electricity.  In that case, the math would show a reduction in the cooling load and production of power, two profits, a direct and an indirect profit.

There are many cases of profit-making, of unintended benefits, of positive externalities, if you wish, and, luckily, the complicated arithmetic has already been done objectively, reliably (see reference).

Two of the many design elements in a neighbourhood development, of which the unaccounted ledger lines could be in the profit column, are trees and parks. Usually they are factored in as the necessary cost of compliance with municipal regulations or a cost for an attractive, picturesque streetscape. 

Research and good math now show that they can be moved from the debit to the credit column: they can earn money in the short and long run. They do so in many ways: by cutting cooling and heating costs; reducing water runoff; reducing garden watering; saving on conveyance piping;  stormwater plant load; capturing and storing CO2 and harmful emissions; reducing ambient temperatures and raising property values and the tax base, without including hard to price health benefits.

Here are some rounded figures of what one tree can do in an average year for a house, a neighbourhood, a municipality and the city:

  • Intercept  9,000 litres (2000 gal) of rainfall
  • Save 200kWh of electricity in cooling
  • Save 3 mil Btu  in heating
  • Capture  0.7 kg of four harmful air pollutants (added for simplicity)
  • Capture  200 kg  of CO2
  • Reduce storm infrastructure costs 
  • Reduce storm end-treatment costs
  • Increase property value near a planted space

To turn all these additive benefits into money, let’s take an example of a 16 ha (40 acre) neighbourhood with 400 houses and 500 trees, some on its streets and some in a local small park. We take the available summary calculations and, using averages for simplicity, we get the following figures separated by the beneficiaries: the homeowner, the developer and the city at large (all of us):

Total monetary gain in savings from 500 trees and a small park:

  • The homeowners get $29,000 in reduced heating and cooling costs combined.
  • The city saves $245,000 in infrastructure costs and $200 in water treatment costs
  • The developer gets a share of the upfront savings in  storm water infrastructure
  • The capture of CO2 saves $1200 and is equivalent to removing  100 cars from the road
  • The capture of harmful pollutants saves $2,200
  • The developer earns an average of 16% sale price premium

    Trees add delight to the street but also value to properties

 

Altogether this neighbourhood would save $267,000 the first year and $32,000 each additional year.  And energy prices go up and the value of carbon increases in trading so will the hidden benefits of this neighbourhood. And we just scratched the surface; more positive outcomes from the avoidance of energy gas production, the water quality benefits the reduced frequency of garden watering and so on the chain continues.

The developer has two additional hidden benefits: An alluring sales pitch and, most likely, faster sales, a critical factor in profitability.

Green profits grow like trees or business, slowly; and they last. No one would plant an olive tree expecting to sell olives a year later. It takes about 10 for the first meagre crop, but the tree can last over 1000 years; it is a long term investment plan; a variety of green chip shares. Same is true for planting trees and creating neighbourhood parks.

These generalized and simplified figures avoid the confusing conditionals that appear in research reports.  They paint the big picture, the order of magnitude of the uncounted benefits. The details may vary in each case. But the overall picture is bright: the veiled currency that has been eluding circulation is green.

 

Reference: Center for Neighbourhood Technology, 2010: The value of green infrastructure

 

Green them and they will walk – How to get people on a healthy path

Planners feel uncomfortable when reading the stats on the prevailing trends in travel:  Car ownership is growing steadily, personal driving is rising, walking and bicycling are declining, and fewer children walk to school. Also discomforting are the stats about increasing levels of obesity among adults and children and the growing number of cases of lung and other complications due to poor air quality.  This unease propels a strong drive to change how communities are planned and built.  Can different planning techniques stall or reverse these trends?

black to green grid
The uniform car grid morphs into a pedestrian haven

Take air pollution for example, some 18% of which stems from personal driving. For their first 80 years in the city, cars were running without catalytic converters; the unhealthy result was inevitable but also unsustainable.  In comes the “cat-con” car in the 80s that reduces smog dramatically; a simple, inexpensive, regulated device with an enormous positive effect; same city, more cars, more driving but far fewer noxious gases. Planners and developers had little to do either with the problem or its solutions. Looking fifty years ahead, fuel-cell, full electric and hybrid cars, now in production, will send fewer or no gases out the exhaust pipe; same city, no pollution.  When driving must be done, improved technology could make it healthier for people and the planet alike.

But rehabilitating the tailpipe still leaves parents, children and everyone else stuck in their cars driving to nearby or long destinations; an unhealthy routine, particularly for children.  Can people be enticed out of their cars and on to their bikes and feet? What do we know about habits, inducements and their influence? What can a developer do about less driving in a new subdivision?

We know that travel to work accounts for about 40% of all driving and understand that shifting it to other means is a long shot. A CMHC study (2010) showed that there was no difference in the use of transit among eight suburban neighbourhoods (at a mere 9%) even though four were designed to be transit-friendly. Evidently, the decisive factors lie outside the developer’s subdivision plans.

Neighbourhood Opportunity

But at the neighbourhood scale, the developer can have an influence. We know increasingly more and with greater accuracy about design features that could lead to more walking in the neighbourhood.  It all rests on two key concepts: connectivity and permeability.  Connectivity translates into how often people can turn a corner within their neighbourhood. If you can count at least 30-to-40 intersections in a square kilometer, check “good”. More is better.  Permeability is about filtering and preferential treatment. When walkers, joggers and cyclists can keep going beyond where cars can, they get an advantage. Research findings confirm that they prefer it that way.  

Filtered permeability can be best grasped with a drawing. It shows a classic uniform grid (Portland) and one possible modification (right) to benefit pedestrians. The grid with its high connectivity (160 intersections per km) remains the same, but half the streets become paths for pedestrians and bikes. Cars have access to all blocks but not all streets. Permeability favours pedestrians; the joy of walking intensifies.

One more idea added to these two completes the enticement platter – proximity.   It means having destinations nearby such as parks, playgrounds, convenience stores, schools, barbers and such.

A street transformed from car-realm to people haven

The good news

The results are in for these three alluring attributes that would predictably and measurably increase walking.

The CMHC study (above) showed that the two layouts with the highest connectivity  scored 100% more walking trips above the average of all eight neighbourhoods and about 300% more than those with the least walking trips. Not only did they have high connectivity, they also had the highest number of pedestrian paths. The positive influence of the paths is made clearer by the contrasting numbers of a neighbourhood with  a low walking score had just as high connectivity as the ones with top walking scores  but  had few pedestrian paths. Connectivity  works best when complemented with paths.

More and precise evidence comes from a Memorial University (2010) study: of seven neighbourhood designs two stand above the rest with 25%  and 32% more walking in the set; both have paths separate from the regular streets . In addition to increasing walking, they also lowered driving by about 10%. 

An earlier CMHC study (2008) found that the presence of separate paths increased walking by 11.3% and its higher pedestrian connectivity reduced local car kilometers by 23%.  Separately, another study concluded that having a recreation, green space close to home would get more young people walking.

Though locally reduced  driving remains in the range of 78 (lowest) to 81(average) percent of all trips. But we can now trust that it is possible to get more people back on their feet. Green their streets and they will walk.

A Street you can call your own

 

There are two languages in currency that we use to talk about streets: one used by people who live on them and another favoured by transportation engineers. The first expresses our experience of streets and the other describes what each does in a “system”, the transportation network system.

People say they live on a “residential” street or a quiet street, on “main” street or a busy street; words that express an atmosphere, a feeling with always a hint of affection or disapproval. In the “system” or “network” these streets could be “local”, “collector” or “arterial”; neutral labels that ascribe daily car volumes, and imply number of lanes and permissible speeds; people and milieu are out of the picture. This impersonal language stems from a gradual shift in the street ownership from full people ownership to shared ownership with the car, the majority holder.

A narrow exclusively pedestrian street that evokes a welcoming feeling

 Streets were places where people strolled, kids played games and tricks, conversations started, adults traded ideas and goods and, occasionally, a spontaneous display of talent took place; that was the “public realm”, fully owned and used by people. A new owner, the car, now claims rights to the street space and a new craft has emerged to accommodate its requirements. Along with the craft came a new language, the “system” language of classification. When it is translated into design on the ground the result is inhospitable, unfriendly, unattractive streetscapes. 

To shape a welcome outcome when planning a street, the question to ask is: Whose street is it? 

To recover the craft of making streets people bond to, the path may start by rediscovering the meaning of original street words and their story. “Avenue,” for example, originally meant an approach leading to a country house, usually framed by a double row of trees. On the map, such an approach would resemble an impasse, a private lane with just one big house on it.  Later, avenue also meant a spacious road with large, shady trees on both sides. But shortly after, seen as serving primarily the car, it lost its trees and turned into a naked, wide, asphalt-and-cement road with up to 25,000 cars passing by each day.  But this need not be the case.

A similar story unfolds around the boulevards. Originally, they were wide promenades that replaced the obsolete fortifications. Fully landscaped, with spacious sidewalks, they created a country-like atmosphere often enhanced by an occasional park. Street crossing happened casually and leisurely anywhere, at whim. And, following the trace of the defence walls, boulevards circled the city. They were so charming and so conducive to socializing that they even generated a new class of citizens, those who frequented them: the boulevardiers. But being wide and continuous, boulevards naturally fell prey to the service of motor transport, losing the atmosphere that made their name synonymous with charm and leisure time. But this need not be the case when designing new ones.

The avenue story tells us about the importance of quiet and nature in a residential street. And since the majority of streets in every city are residential, there is a lot of opportunity for innovation. First, limit car access to residents-only or make them entirely pedestrian. People-permeable cul-de-sacs or loops do this well. Then use mostly 3-way intersections and use turns to slow cars down. Be generous with tree planting. Nothing surpasses the delight and comfort of a street that has been canopied over by a double row of trees. With these elements in place, majority ownership shifts to residents; and they love it. It sounds almost too good to be practical. Yet this is exactly what was built in Vauban, Germany and it changed our  perception of what’s possible.

The boulevard story brings the message of space, plenty of space – for people. When planning them, change the balance between car and people space. Instead of the now usual four or six car lanes to one half equivalent people-space on the sides, make it four to one or to two. Similarly, when six lanes are allocated to the car, give two or three to people, a la Champs Elysees. This means a virtual linear park on either side of the boulevard with three or more rows of trees and a bike path separate from the road. Add trees and shrubs to a wide median also. The traffic is still there, but now people have plenty of room to walk, stroll, loiter and chat in a charming milieu, their own realm. Alternatively, separate the two streams of traffic by a building block and fill it with a variety of public spaces that make it a predominantly pedestrian area.

Using these techniques, streets can become places that people can call their own.

Portland’s Portal of Opportunity – The Multimodal Grid

In an earlier article about the Portland grid, we identified a number of its shortcomings and speculated that they may be the reason it has not been replicated; no other discernible obstacles would seem to block the way and praise of it has been plentiful.  In the meantime, research and events recast the Portland grid as a potential ground for a pioneering transformation. Such a remoulding can sharpen Portland’s already strong profile as a center of urbanism that transcends mere historicism and becomes fully contemporary.

Research and Events

The earlier article noted that Portland’s praised intersection (140 per km2) and street density comes at a heavy cost.  It means reduced developable land, higher infrastructure cost, higher lifecycle costs, reduced traffic flow and safety, reduced rainwater permeability and fewer opportunities for public open space.

 Figure 1. The Portland Grid and Ladd’s Addition layouts – same scale

While the article recognized the grid’s high legibility and walkability, it pointed out that these valued characteristics were, evidently, insufficient to create a following. There has been no copy of it in North America or elsewhere since 1866.  We observed that even in Portland itself, and shortly after its platting, deviations from its stereotypical grid started to emerge, an example of which is Ladd’s Addition (1891). It turns out this Addition was an extraordinary and remarkable deviation.

By coincidence, as our critique surfaced, APA named Ladd’s Addition “a great neighbourhood” under their ongoing program that recognizes planning achievements.  Then new research appeared on “Emergent Neighbourhoods” (EN) by four well-known urbanists that revealed the 400-m rule and the importance of “sanctuaries”.  Ladd’s neighbourhood, it would seem, is a living demonstration of these two concepts.                                                                                                                             

The “great neighbourhood” designation and the new research findings spurred a revisit of the Portland grid with a focus on a potential transformation that would amend its weaknesses and in the process of doing so offer a template for other existing cities that are laid out in uniform, undifferentiated grids.  This re-think also responds, belatedly, to a challenging comment: “….Rather than this grab-bag of criticisms, it would be more useful to develop a consistent positive alternative to the Portland grid”.

The ushers of opportunity

The APA follows a rigorous selection process and uses a clear set of criteria for awarding a neighbourhood the status of “great”. In the case of Ladd’s Neighbourhood the rationale presented for awarding the title was as follows:

  • Departs from the common uniform grid
  • Includes a hierarchy of streets
  • Defines neighbourhood boundaries clearly
  • Prevents cut-through traffic
  • Prevents higher density
  • Buffers pedestrians with ample street landscaping
  • Influenced New Urbanist plans such as Fairview Village, Orenco Station and Seaside FL

The departure from the uniform grid is said to have been inspired by the L’Enfant plan for Washington and the related “cities beautiful” movement.  It would appear that in the ex-Mayor’s cultural frame of reference of the 1880s, the uniform grid lacked the ingredients that would enhance beauty in a neighbourhood. Most contemporary planners seem to agree with Ladd’s assessment as they rarely, if ever, produce uniform, orthogonal grids.  Ladd, as a land owner and successful businessman, may have also discerned the land use inefficiency of the Portland grid; his neighbourhood blocks are, on average, at least twice the size and the street density considerably lower than the surrounding districts (Figure 1). Contemporary planners followed in Ladd’s steps with even larger blocks for the same reason.

The hierarchy of streets in an era of horse, cart and coach would seem hardly necessary as neither the traffic volume nor its speed would be sufficient to justify it; they bear no comparison with contemporary numbers that are at least an order of magnitude higher.

Moreover, this was a subdivision carved out of farmland and Douglas fir forest across the river away from the city. It was intended as an exclusive residential enclave for wealthy Portlanders who sought a quiet place in the “country” (1891). Whatever the original motivation, the hierarchy of streets serves the neighbourhood well 100 years hence; yet, evidently, not well enough.

Even though the disruption of the surrounding grid inevitably prevents direct flow of through traffic (another APA point of recognition), it did not do it adequately until after residents and the City introduced additional exclusion and diversion measures to achieve a dramatic, and welcome, reduction from 6,000 ADT to 1500 ADT.

By virtue of the disruption of the grid, the boundaries of this neighbourhood confront the driver boldly.  Most of the surrounding streets terminate at these boundaries signalling an enclave, a “sanctuary” that one has to circumvent. Navigating through its four quadrants can be confusing to a visitor since the plan defies the familiar orthogonal geometry, even though all its streets are rectilinear and none a dead-end.

Having a strong sense of community identity and an appreciation of its valued attributes, residents fought and achieved a down-zoning of its future density. Though by no means urban at 7 dwelling units per acre (18 per ha), it seems to produce a satisfying milieu. The residents have embraced the result and the APA lauds their strong attachment.

Emergent Neighbourhood Research

Characterizing the boundary thoroughfares and quiet enclaves as “natural”, new research on Emergent Neighbourhoods (EN) presents the case of the 400 m spacing rule and the “sanctuary” as organizing principles of existing city districts. Both principles can be seen in Ladd’s addition. It is about 800 m long by 600 m wide and bisected in both directions at half points with straight through streets, with an interrupting large, landscaped roundabout. Thus four “neighbourhoods”, quadrants, or “sanctuaries” are created.

The 400m rule reflects the finding that communities tend to include significant thoroughfares that are endowed with services at about 400 m intervals. The areas enclosed by them are primarily residential and their street pattern discourages non-residents from going through the loosely defined enclave.  The authors argue that if such a pattern of self organization can be observed almost universally, it might be a useful blueprint for planners to follow in layouts for new districts. Were planners to do so, they would be simply applying an “organic” formula that has been tested by time and proven to work.

From the perspective of this EN research, the uniform Portland grid is uncharacteristic (one might say unnatural) and unable to follow the 400 m rule or to form ‘sanctuaries’. Its

unnaturalness may be unsurprising when one considers that it was a speculator’s and land surveyor’s preferred method of layout: simple, repetitive, fast and less prone to boundary disputes. Contrary to the examples, cited in the EN research, that emerged organically, the grid was a “rational”, imposed solution.

Biophilia and Patterns

Recent research has established that humans take pleasure in being in nature and that natural setting and living things can have a therapeutic influence on people. This affinity and relationship is thought to be based on man’s common chain of evolution with all living things. Critics see some urban conditions as the cause of what is termed “nature deficit’. An extension of this connection with nature is the proposition that human artefacts, including cities, often exhibit the geometry of living organisms.  In that geometry, the parts do not make a whole, it is the whole that shapes the parts in constant co-evolution. (mehaffy?)

The elements of transformation

To these germane ideas, 400m-rule, sanctuaries, departure from the grid, biophilia and the whole-part relationship one must add three others by C. Alexander, whom the EN research authors revere as a mentor. Alexander argued that roads within a neighbourhood should be discontinuous to induce the sanctuary atmosphere and to that end he proposed patterns that relate to vehicular and pedestrian movement: Pattern 49 (Looped Streets), Pattern 51 (Green Streets) and Pattern 52 (Paths and Cars).

 

By coincidence, as our critique surfaced, APA named Ladd’s Addition “a great neighbourhood” under their ongoing program that recognizes planning achievements.  Then new research appeared on “Emergent Neighbourhoods” (EN) by four well-known urbanists that revealed the 400-m rule and the importance of “sanctuaries”.  Ladd’s neighbourhood, it would seem, is a living demonstration of these two concepts.

The “great neighbourhood” designation and the new research findings spurred a revisit of the Portland grid with a focus on a potential transformation that would amend its weaknesses and in the process of doing so offer a template for other existing cities that are laid out in uniform, undifferentiated grids.  This re-think also responds, belatedly, to a challenging comment: “….Rather than this grab-bag of criticisms, it would be more useful to develop a consistent positive alternative to the Portland grid”.

The ushers of opportunity

The APA follows a rigorous selection process and uses a clear set of criteria for awarding a neighbourhood the status of “great”. In the case of Ladd’s Neighbourhood the rationale presented for awarding the title was as follows:

·         Departs from the common uniform grid

·         Includes a hierarchy of streets

·         Defines neighbourhood boundaries clearly

·         Prevents cut-through traffic

·         Prevents higher density

·         Buffers pedestrians with ample street landscaping

·         Influenced New Urbanist plans such as Fairview Village, Orenco Station and Seaside FL

The departure from the uniform grid is said to have been inspired by the L’Enfant plan for Washington and the related “cities beautiful” movement.  It would appear that in the ex-Mayor’s cultural frame of reference of the 1880s, the uniform grid lacked the ingredients that would enhance beauty in a neighbourhood. Most contemporary planners seem to agree with Ladd’s assessment as they rarely, if ever, produce uniform, orthogonal grids.  Ladd, as a land owner and successful businessman, may have also discerned the land use inefficiency of the Portland grid; his neighbourhood blocks are, on average, at least twice the size and the street density considerably lower than the surrounding districts (Figure 1). Contemporary planners followed in Ladd’s steps with even larger blocks for the same reason.

The hierarchy of streets in an era of horse, cart and coach would seem hardly necessary as neither the traffic volume nor its speed would be sufficient to justify it; they bear no comparison with contemporary numbers that are at least an order of magnitude higher. 

Moreover, this was a subdivision carved out of farmland and Douglas fir forest across the river away from the city. It was intended as an exclusive residential enclave for wealthy Portlanders who sought a quiet place in the “country” (1891). Whatever the original motivation, the hierarchy of streets serves the neighbourhood well 100 years hence; yet, evidently, not well enough.

Even though the disruption of the surrounding grid inevitably prevents direct flow of through traffic (another APA point of recognition), it did not do it adequately until after residents and the City introduced additional exclusion and diversion measures to achieve a dramatic, and welcome, reduction from 6,000 ADT to 1500 ADT.

By virtue of the disruption of the grid, the boundaries of this neighbourhood confront the driver boldly.  Most of the surrounding streets terminate at these boundaries signalling an enclave, a “sanctuary” that one has to circumvent. Navigating through its four quadrants can be confusing to a visitor since the plan defies the familiar orthogonal geometry, even though all its streets are rectilinear and none a dead-end.

Having a strong sense of community identity and an appreciation of its valued attributes, residents fought and achieved a down-zoning of its future density. Though by no means urban at 7 dwelling units per acre (18 per ha), it seems to produce a satisfying milieu. The residents have embraced the result and the APA lauds their strong attachment.

Emergent Neighbourhood Research

Characterizing the boundary thoroughfares and quiet enclaves as “natural”, new research on Emergent Neighbourhoods (EN) presents the case of the 400 m spacing rule and the “sanctuary” as organizing principles of existing city districts. Both principles can be seen in Ladd’s addition. It is about 800 m long by 600 m wide and bisected in both directions at half points with straight through streets, with an interrupting large, landscaped roundabout. Thus four “neighbourhoods”, quadrants, or “sanctuaries” are created.

The 400m rule reflects the finding that communities tend to include significant thoroughfares that are endowed with services at about 400 m intervals. The areas enclosed by them are primarily residential and their street pattern discourages non-residents from going through the loosely defined enclave.  The authors argue that if such a pattern of self organization can be observed almost universally, it might be a useful blueprint for planners to follow in layouts for new districts. Were planners to do so, they would be simply applying an “organic” formula that has been tested by time and proven to work.

From the perspective of this EN research, the uniform Portland grid is uncharacteristic (one might say unnatural) and unable to follow the 400 m rule or to form ‘sanctuaries’. Its 

Biophilia and Patterns

Recent research has established that humans take pleasure in being in nature and that natural setting and living things can have a therapeutic influence on people. This affinity and relationship is thought to be based on man’s common chain of evolution with all living things. Critics see some urban conditions as the cause of what is termed “nature deficit’. An extension of this connection with nature is the proposition that human artefacts, including cities, often exhibit the geometry of living organisms.  In that geometry, the parts do not make a whole, it is the whole that shapes the parts in constant co-evolution. (mehaffy?)

The elements of transformation

To these germane ideas, 400m-rule, sanctuaries, departure from the grid, biophilia and the whole-part relationship one must add three others by C. Alexander, whom the EN research authors revere as a mentor. Alexander argued that roads within a neighbourhood should be discontinuous to induce the sanctuary atmosphere and to that end he proposed patterns that relate to vehicular and pedestrian movement: Pattern 49 (Looped Streets), Pattern 51 (Green Streets) and Pattern 52 (Paths and Cars).

Figure 2(after Alexander):  Paths and Cars – #52 : left, roads only, right, with overlaid paths

The latter pattern states that the recommended way to lay out pedestrian paths is to have them run independently and perpendicularly to roads, wherever possible (Fig 2).

 A Portal of Opportunity

The APA rationale combined with the Emergent Neighbourhood research findings and Alexander’s patterns generate a set of guidelines that lay the foundation for Portland’s portal of opportunity:

·         Apply the Ladd’s neighbourhood logic to other existing residential neighbourhoods

·         Use the organic rules of “sanctuaries” and main thoroughfare spacing

·         Apply Alexander’s patterns at the sanctuary scale

Ideally, Portland’s residential districts would be reorganized into multiple Ladd’s neighbourhoods; an attractive proposition but clearly a theoretical speculation at best. However, another alternative that draws lessons from Portland itself, particularly the Pearl District, and from European city cores can form the basis for an alternative, pragmatic  transformation. 

  

Figure 3. One of Pearl District’s Green Streets (Google street view)

In the Pearl district a number of streets have been closed to traffic to great advantage and delight. Similar closures have occurred elsewhere sporadically in Portland. More extensive closures have occurred in the central areas of small and large European cities such as Strasburg, Montpellier, Munich, Athens and others. Many of these reclaimed streets are predominantly residential with an occasional mixed use on the ground floor. In addition to full closures, there have been partial and controlled, managed closures. (see Fig. 6 from Paris)

Using the full panoply of these ideas and practical measures, Portland is uniquely positioned to transform its residential districts into multiple, virtual Ladd’s Additions while leaving the entire infrastructure and real estate intact. These new districts would represent an evolution of its grid, an adaptation to the contemporary means of transport and to the environmental imperatives of less driving, more walking and greater water retention on site: From a uni-modal grid, dominated by motorized mobility to a                                           

 

                            Figure 5: Transcending the Portland grid: Left, the uni-modal grid and Right, transformed into a multi-modal, fused grid.

multi-modal grid where natural mobility reclaims its share of the neighbourhood network.

 Figure 5 shows one of many possible end-states of transformation. In this version:

·         The neighbourhood or ‘sanctuary’ measures 400 m by 400 m as the research suggests

·         It is about one quarter of the total Ladd’s Neighbourhood area. Consequently four such units with a central traffic circle would amount to a larger identifiable neighbourhood.

·         The sanctuary is impermeable to cars and fully permeable for pedestrians

·         Traffic loops  are used, an Alexander pattern ( #49) to achieve traffic  impermeability

·         The paths and roads are set at right angles, pattern #52 but occasionally overlap

·         Introduces  several ‘green streets’ (pattern #51)

                                                        The resulting reconfigured pattern retains the full connectivity of the original as all blocks and streets are preserved intact along with their intersection density. While retaining the original advantages of connectivity and route directness, the transformation enhances the pedestrian environment appreciably and offers many more open and play space opportunities. A basic calculation shows that the reclaimed Right Of Way will add 5.5 acres of open space the equivalent of about five city blocks or about 14% of the total neighbourhood area of 40 acres. If only the reclaimed asphalt pavement were counted, the resulting reclaimed ground is 1.8 acres or about two city blocks. In addition, it renders the Portland grid far more environmentally responsive through a two-fold increase in permeability. Moreover, it would demonstrate unambiguously that it is possible to start with a rational speculator’s grid and arrive at an ‘organic’ pattern.

Figure 6. Controlled access with retractable bollards – a management approach to transforming streets. (note the discontinuous sidewalk on the left)

This example simply sets out a logical sequence of displacing asphalt with landscaping in a way that streets and paths are direct and interconnected. One sanctuary at a time, large residential districts can become the newest Ladd’s Additions of Portland.

Inevitably, the question of traffic surfaces. The Ladd’s district traffic calming initiative provides the answer. However, in this case, the new plan has unparalleled inherent flexibility, unlike its inspirational model. Should additional streets be needed to accommodate growth and traffic flow, at some future date, returning carefully selected streets, according to need, to their original asphalt state would encounter few difficulties. The City has unfettered jurisdictional power over streets, a public domain, to implement any desired transformations deemed to be in the public good.

Such initiative would not be exceptional. Several European cities have dealt with large downtown areas that had complex, labyrinthine networks and significant build infrastructure of historic value. (see Bremen, GM for example) They all accommodated traffic and services through careful planning and management.

                                         This transformation might also serve for another form of evolution. If later in the century some of the transformed neighbourhoods become subject to strong intensification pressure, the  green streets can be built above and become  “stoas” – full-fledged passages through the building (following the street’s ROW alignment) that perform all the functions of a street – except car movement. Interestingly, these will materialize yet another of Alexander’s patterns – Building Thoroughfare (#101). Not only would these new type of connectors add variety (and protection) in the build environment; they would also earn real estate income for the city.  Symbolically, these will be the portals to future urban landscapes

Figure 7. The old city centre of Bremen, Germany uses a blended network of car (blue) and pedestrian streets (green) to transform the area into a pedestrian haven. (Google Earth images)

 In summary, according to credible research and obvious arithmetic these measures will:

·         Increase walking and reduce driving

·         Increase area permeability by reducing asphalt

·         Reduce water outflow by way of the new permeable surfaces and trees

·         Provide sociable space and areas for safe play

·         Increase property values within the sanctuaries

·         Increase the attraction of the City to suburban residents.

Such a transformation could re-position Portland as a leader in urban thinking and provide a  template for change in other gridded cities. It will prove that Portland’s less than meritorious grid has one unique merit: adaptability to new urban requirements and environmental imperatives. Its grid, morphs into portal of opportunity.

Figure 8.  “Stoa”  -  A through-the-building arcade that connects two parallel streets.
Figure 8. “Stoa” – A through-the-building arcade that connects two parallel streets.

 

 

 

 

 

 

 

 

 

 

 

Fanis Grammenos

This article first appeared in Planetizen.com in April 2011

Previous article:                             http://www.planetizen.com/node/41290

APA recognition site:                   http://www.planning.org/greatplaces/neighborhoods/2009/

Emergent Neighbourhoods:   Michael Mehaffy, Sergio Porta, Yodan Rofe and Nikos Salingaros: Urban nuclei and the geometry of streets, 2010 , Urban Design International Vol. 15, 1, 22–46 45

 

 

European Urbanism: Lessons from a City without Suburbs

Introduction

Planners despise, deride and deplore the suburbs. Suburbs are portrayed as the pariahs of urban evolution, an aberrant, ill-adapted species and the main cause of problems that beset cities and people today such as traffic congestion, poor air quality, environmental degradation, ugliness and even obesity. Their critics recommend a halt to new ones, a retrofit of the existing and putting an end to the idea of the “suburban project” once and for all. Discomfortingly, new ones are nonetheless approved daily.

Urbanizing the suburbs, it is argued, would enable city residents to enjoy a better, healthier more fulfilling life in a continuous city that spans an entire urban region. Moreover, the environment will also benefit from reduced travel emissions. What would a city that spans a region be like? Can it be planned for?

While searching for policies and levers to stem new or to retrofit existing suburbs, it might also be instructive to look for precedents, real examples of a city as it would be on arrival at the “end of the suburban project”. Precedents not only would lure planners and people by the power of their images but could also become practical guides. A contemporary precedent, were it to be found, would have great convincing power since it would have dealt with the modern issues of mobility, accessibility and commerce.

Reassuringly, at least one such city does exist: one that has reformed its suburbs to the point where they are indistinguishable from the mother “city” – Athens, Greece. This article looks at this example, attempts to draw lessons and raises disquieting questions.

Before looking at Athens, let’s make a parenthetical agreement.

Agreeing on “city

Of all the attributes that characterize a city, there can be little doubt that proximity is the most crucial because of its generative power: building and population density,  compactness of built form,  concentration of people,  nearness and choice of desired destinations and the constant buzz of transaction and interaction are all expressions of proximity and its outcomes.  Its iconic expression is found in the agglutinated forms of earlier cities where city blocks had complete, solid perimeters, and in their crowded markets.

Agglutination and compactness appeared early on in “organic” and planned settlements from Mohenjo-Daro (2000 BC), to El-Lahun, Egypt (1885 BC) to Miletus, Greece (500 BC) and Pompeii, Rome (100 BC). Population density in the Greek and Roman towns was 200 and 170 persons per hectare (ppha) respectively, while the Italian City State and the medieval cathedral city posted 75 and 110 ppha respectively. By contrast and for context, the city of Toronto in 2001, posts much lower average at 40 ppha, but reaches 90 ppha around the core. Toronto is a young, mainly 20th century city; a new urban species.

FishMarket

The 20th century brought separation and dispersal of buildings to an extent unparalleled in city history.  Aerial photos and ground observation confirm this unambiguously – the sharp contrast of built form between the old “city” and its newer additions is inescapable.  However, the 20th century also ushered a new form of agglutinated settlement, the vertical, elevator block, which can equal several earlier horizontal blocks in habitable space and thus dramatically increase the potential for people concentration.  Athens employs all the elements of propinquity and can boast being a contemporary pioneering example of “a city without suburbs”.

The density story of Athens

Being a typical old city, Athens started as a small dense settlement which remained the focal point of a radial expansion and the locus of gradual increases in density over its subsequent evolution.  Since becoming the capital and a main industrial and commercial hub (1836), its trajectory as an urbanized region followed that of other major European and American cities. It traces the continual intensification of land use at the centre and of adjacent land parcels in ever widening circles. This gradual expansion also saw the creation of suburbs that incorporated a preponderance of detached private homes, not unlike other European and North American cities. Occasionally it subsumed pre-existing villages that had small populations, dispersed buildings and an agricultural economic base.  Two other events also shaped the growth of the city: Illegal, usually dense, settlements of massive scale that were later brought within the regional plan and large population in migrations due to political instability.

Central city density

Athens’ population growth to its current 3.1 million follows an exponential curve similar to metro areas elsewhere that saw their populations swell in the 20th century. But the average density of Athens increased proportionately in step with its population growth while, by contrast, in other metropolises average densities either rose only slightly or remained stable. In 2001 it stood at 76 ppha as compared to the average 40 ppha and 30 ppha of Toronto and Philadelphia (1991) respectively, two prime examples of compact cities in North America.

Indicatively, the CBDs of these two cities post densities of about 75 and 79 ppha surprisingly similar to the average built-up area density of Athens. Other CBD densities in North America range from 17 ppha in Atlanta to 55 ppha in Vancouver. Evidently, in the case of Athens, the large increase in population was accommodated by compaction and an upward expansion.

The eradication of suburbs    

Average city densities hide the potential for sharp differences between centre and peripheral districts, which could still post low enough densities to qualify as suburbs or “sprawl”.Statistics show that in 2001 just four of about 30 boundary municipal districts, about 6 to 13 km from the centre, had densities between 25 – 50 residents per hectare,  higher than the CBD density of Denver, Detroit, Washington, Seattle, Atlanta and Houston.

Seven other districts, also at the edge, record densities of 50 to 100 people per ha and the remainding 37 of the total 48 districts surrounding the central area, from 100 to 250.  These peripheral, euphemistically “suburban” densities equal or are multiples of CBD densities of many metros in the US and Canada. Clearly, this 40-year long transformation of what used to be first and second ring low density settlements has eclipsed any semblance of “suburb”. Aerial and site photos confirm this compactness of the built environment.

 Detached single family houses are a statistical rarity; mostly aged holdouts or derelict sites awaiting development. Compactness, a key element of urbanism, has reached appreciably high levels and Athens is now in essence 412 square kilometres of “city” by any measure.

Land use propinquity

As might be expected, with contiguous high concentrations of people, city services and amenities proliferate: transit, small or large retail, and a range of outlets that cover the entire gamut of daily and longer-cycle needs. Most collector and arterial roads boast a continuous line of shops and work places on the ground floor. This alternate use of the ground floor is so extensive and liberal that even in the outer ring districts one finds shops and workshops as unusual as a car repair shop and an ironworks on residential streets.

Ironworks shop on suburban street – sidewalk overtaken

Transit service has traditionally been good and it was recently enhanced with the addition of a new Metro (subway) and complementary light rail lines. Accessibility is high and distances to services are within the five to ten minute radiuses that render each neighbourhood eminently walkable.  Walkability is further enhanced by the narrowness of most streets and the scarcity of wide arterials.

Design and diversity

The gradual but continual redevelopment of urban lots brought to the same street vogues of architectural styles that increase building diversity and interest. This diversity is enhanced by the dominance of lot by lot development that prevents the monotony and discomforting scale of large structures, which are rare. The street facade, mostly contiguous, is a sequence of 60 to 100 feet tableaus of fashionable or individual tastes from period eclectic to Bauhaus and to post-modern. Housing type diversity, however, is absent as the choice is limited to apartment size and price; other types are few and scarce.  As for social diversity, the mix is much less extensive. The map of residential districts is to a large extent also a map of social classes. Planners and policies have been virtually powerless in controlling social self-selection and exclusion. (Interestingly, Hippodamus (450 BC), often called the father of planning, advocated the idea of segmenting a city area into social class districts.)

All the elements of urbanism for good living are present: Density, Diversity, Destinations, Distance (to transit) and Design; the same ingredients that are theoretically essential for reducing the environmental impact of development, primarily by reducing personal car use. Moreover, suburban sprawl has been expunged. Is Athens, then, a European poster child of advanced urbanism? a coveted future of all urban regions?

How this level of urbanism was achieved, how the city measures up with the current environmental priorities and how living in this environment enhances the lives of its inhabitants are all subjects for what follows.

The drivers of change – density

The trend towards eradicating the suburbs started in the 70s. There was no “ideal city” image or planning theory that drove the transformation (TND or New Urbanism had not been invented yet). Most planning efforts were focused on maintaining the strict height limit, preserving and enhancing open space and, more intently, on designing and implementing a transportation network that would solve the persistent gridlock that emerged early at comparatively low car ownership ratios. The densification trend sped up in the 80s, and currently continues at the periphery.

The trend toward intensification may be attributed to a) a geographically confined land supply (mountain and sea boundaries), b) a political lesser-faire ideology, c) a powerful, well-connected developer lobby and d) enormous population pressures due to constant in migration. The most critical factor, however, was the legislation passed by a dictatorial junta at a pivotal point (1968). The decree raised the FSI by 30% uniformly overnight. This increase in turn triggered a lucrative construction boom of apartments to satisfy the latent demand and the constant in flow of workers. It also meant increased unit and population density as the scarcity of habitable space and its cost forced traditionally large households into small apartments .  The comparison of the GDP in conjunction with density (Fig 7) hints at a potential correlation between income and density that is worth noting in this case even though it may not apply universally.

Elements of urbanism and performance

Transportation

A key driver in pursuing urbanist policies and  guidelines is to reduce personal car travel and, possibly, car ownership rates. It has been estimated that both the number of trips and total VKTs will be lower among people who live in cities or neighbourhoods that have the Athenian characteristics of density, street connectivity and mixed use. Speculatively, doubling the densities of urban regions (in the US for example) and complementing it with mix of uses will reduce personal VKTs by 10% in  20 years. What do Athenian statistics tell us about these relationships?

Car and Powered Two Wheeler (PTW) ownership

 Between 1990 and 1999, the number of private cars increased by an average of 60,000 per year from 800,000 to 1,400,000 units, for a total of 75% increase. However, Athens still has the second lowest rate among the EU cities at 339 per thousand people above Madrid at 322. By contrast, ownership of PTW is the second highest after Rome and, at 58 per 1000 people, is 3 times that of Paris and twice that of Madrid’s rate. The high PTW rate may be the effect of income and also choice. PTW cost half to one third the price of cars and, therefore, could be popular among less affluent would-be car drivers. The choice of  PTWs is also clear on the grounds of their flexibility as means of personal transport in a congested city; they hardly ever need to wait in line and, occasionally, not even for the traffic lights and can park practically anywhere.  A further reason could be their use as a second vehicle since cars can enter the central city cordon only on alternate days based on their licence plate number.

Figure 9 shows respective ownership figures of EU cities and confirms a well established relationship between wealth and car ownership. The low car ownership rate among Athenians mirrors their GDP. But the city’s compactness, mix of uses, and walkability which have been rising steadily since the 1970s, appears to have had no stabilizing effect on the increase in car ownership or the car modal share. Athens’ motorized transport (cars and PTW) mode share is the second highest after Rome and stands at 52%. The proportion of trips made by car increased in all seven European cities in an interval of ten years but saw its largest increase in Athens at 7% . Athens has the second highest rank of km per person, when adjusted to reflect purchasing power parity (PPP), and the lowest km per person in transit use. This combination results in the highest ratio of car driven kilometres to total motorized trip kilometres.

But if the rising urbanism did not affect car ownership or car trip share, it could, according to earlier research findings, have had a positive influence on the mode shares of walking, cycling and transit.

Transit use, Walking and cycling

The Public Transit share of all trips in Athens is the highest among the European group. Figure 8 indicates a potential correlation between income and public transit use. The fact that Madrid and Barcelona have higher densities, a positive pull on transit, reinforces the link to income. If density were the stronger pull and other things being equal, transit use in these two cities ought to have been at least equal or higher than Athens’.

Transit use has been historically high in Athens all through the 70s and 80s when car and PTW ownership was very low.  The most recent indication of a trend is toward a smaller share. In the 10 years between 1990 and 2000 the share of public transit fell by 7% while private transport increased by an equal percentage. A related statistic indicates that approximately 9,000 bus users shift to private cars every year.This is counterintuitive given the increase in density and mixed use. Moreover, the growing congestion in the centre ought to have acted as a countervailing force to shift car trips to transit. None of these factors seem to have produced the anticipated result of an increased transit and reduced car modal share.

Theoretical analyses and partial empirical evidence link good street connectivity to more cycling and walking in the presence of density and a mix of land uses. Intersection density per km2(a reliable measure of connectivity) of two random Athenian districts of first and second tier rings stands at 130 and 145 higher than good NA grids such as Houston at 90 and Sacramento at 43. Barcelona’s grid sits at 84 intersections per km2. .

Athens’ share of trips made by walking and biking combined is the lowest among the seven Europeancities and is mostly comprised of walking. Cycling, which used to attract large numbers of blue and white collar workers in the 60s and 70s, has become statistically insignificant. Unlike car and transit use that show a potential correlation to wealth, biking and walking appear unrelated. Density also appears unrelated as the three densest cities Barcelona, Madrid and Athens have vastly different percentages of bike/walk shares. These differences suggest that other factors are at play.

It would seem from the above trends that the level of urbanism achieved in Athens did not translate into the expected results in transit, walking and biking activity.

High street connectivity associated with grid-like layouts, such as the layout of Athens’ districts is also said to reduce congestion on collectors and arterials, as cars have a choice of multiple routes to a given destination.  Is this the case with Athens?

Congestion

The Athenian street network is a collection of grid-like configurations with a variety of frequencies and block sizes lacking the familiar N American suburban hierarchy of local, collector and arterial road. In addition, cul-de-sacs are a statistical rarity. Moreover, Athens has the highest length of roads per 1000 population of all seven cities at 4.500 km, implying a very dense grid and small blocks, a recommended practice for walkable urbanism, as is the high proportion of narrow streets.

With these anti-congestion, walkable, network design features, Athens reports the worst congestion in the sample, with lower than expected speeds for given levels of road utilisation among the set.

Interestingly, the city with the lowest congestion level, Barcelona, is also a grid. By comparison to Athens it has the lowest length of roads of the set at almost one quarter of the Athenian rate.  It also falls below Athens in the number of motorways. The difference becomes more intriguing when Barcelona’s higher number of cars is taken into account.

In contrast to the Athenian urbanism, Barcelona’s gridiron has three unusual characteristics: a) block sizes are the largest (113 x 113 m) of all seven cities b) streets are wide (20 m) and the main arterials very wide (50 m) c) all blocks have truncated corners and d) wide diagonal arterials that cut through the entire city toward the centre. These design attributes, hierarchy by size; width of ROW; the large truncated blocks; the directness of the wide diagonals may play a role in lowering congestion. If they can be shown to have a positive influence, then the Athenian version of urbanism of narrow streets, high street density, small block size and non-hierarchical structure, should be re-examined. In fact, support for the need for re-examination comes, surprisingly, from the City of Barcelona itself. Current proposals suggest an increase of the effective size of its city blocks, the largest among the sample, by transforming every second grid street into mainly pedestrian and access only.

Parking 

Athens is effectively an immense parking lot form edge to edge. Three quarters of its streets offer free parking while the rest are frequently used for parking illegally. (Picture of missing tooth)

This is also true of sidewalks, where cars or PTW in particular, find expedient temporary parking. The demand is so high that cars are often parked up to or into the street corner.  It would seem that the available parking in structures is not used to capacity, presumably due to cost. A large percentage of parking (80%) occurs on the street. Of all street parking 45% is illegal.

Parking at this intensity uses up vital road network space that is already constrained due to the narrow width of pavements. A 1998 survey revealed that the daily demand within the city centre during the peak hours is for 66,000 parking stalls and the available supply is 58,000 stalls. It is logical to conjecture a potential link between the parking intrusion into circulation space and the high congestion that Athens experiences, notwithstanding that other factors can also be at play.

By comparison, Barcelona with the lowest congestion level among the seven provides twice as much parking as Athens and holds the top place of parking availability. Constraining parking as a strategy to reduce car use, an often recommended urbanist policy, may lead to unpalatable traffic conditions and their side effects, as the case of Athens would suggest.

Traffic Accidents 

Athens holds the top place in the set of EU countries for traffic deaths.  In Athens, 8,200 accidents occur every year of which 300 are fatal. Interestingly, the three densest cities of the seven also have the high traffic accident incidence even though they have lower car ownership rates compared to the other four suggesting a potential correlation.  Further increase in car ownership, which, evidently, is occurring, may exacerbate the conditions and increase the toll, if it is not matched with proactive measures to improve parking and traffic conditions. The densely packed vibrant streets may hide unpleasant consequences.

Air Pollution 

Perhaps linked with the high congestion but not exclusively, Athens also holds the unenviable top place in pollutant emissions. By comparison, the least congested city, Barcelona, even though denser than Athens and with more cars on the road, shows the lowest pollutant production, less than one quarter of Athens and half or less than London, Paris and Rome.  The Athens figures represent measurements after the extensive catalytic conversion drive, which occurred in the 90s.

Clearly, the Athenian version of a compact, dense, vibrant city may conceal unpleasant negative health and safety consequences apart from potential dissatisfaction with the living environment.

Quality of life  

Urbanism aims at an improvement in the overall quality of urban life from the current state of suburb-centric living, while also pursuing environmental objectives. Measuring quality of life is complex and risky but also necessary, if we are to assert that progress is being made. Several urban criteria are generally used including walkability, sociability, noise, clean air, views, green spaces, and collisions among others.

Noise Pollution 

Driven by the known detrimental health effects of noise, several EU Cities, including London and Paris have begun to map noise levels in their districts. There is general agreement that at 60 decibels noise becomes a nuisance and above 70 decibels it starts to affect the health of residents experiencing it.

A survey in the year 2000 showed that more than 60% of Athenians are exposed to high levels of noise which, on the most congested roads, has been measured to range between 80 and 100 dB during the day but also intermittently during night hours.  Affluent residents find temporary, year round respite from the noise pollution on weekends at their cottages in the coastal areas, a trend that exacerbates congestion and air pollution for the city as a whole.

Open Space and Views 

Athenians climb the coastal mountains to enjoy views and fresh air

A large proportion of Athenians live in 4 to 6 storey apartment buildings and many others in 8 -storey. Due to the narrowness of most streets, the high permissible site coverage and the contiguity of buildings (that in many cases form an uninterrupted “urban wall”) the views for most dwellers are limited to the fronts or the backs of other apartments.  Inhabitants of lower floors of such buildings often miss even a view of the sky. This lack of contact with nature is further aggravated for a large proportion of residents by the absence of urban parks or vegetation on the street. Most buildings have no front yard, and, when they do, many assign it to parking. In addition most sidewalks are too narrow to accommodate substantial vegetation and the dusty, polluted air stresses the plants; they rarely survive to maturity. An additional stressor is low annual rainfall exacerbated by the very high percentage of impermeable surfaces that flush rainwater. In all, the general urban ambiance is devoid of natural features and the residents are deprived casual contact with nature and the pleasure it evokes.

Family life and identity 

Sociologists often point to the unsuitability of apartment living for raising children, particularly in the absence of nearby open space. They also point out the importance of the house as an artefact that supports a person’s identity and sense of self worth. These aspects of psychological reinforcement and satisfaction are by necessity absent in compact apartment living such as in Athens.

Overall Quality of life  

Comparisons between Athens and other cities are unfavourable when quality of life is measured. A casual assessment by a well known urbanist echoes this: “….. as an Athenian I love Athens. But

if you have to live there, the noise, traffic and pollution [would] drive you crazy!” Comparative rankings by established agencies, though inevitably non-scientific, are less casual and at least indicative of the potential quality of a city’s living environment.

The 2008 Mercer evaluation for the top 50 cities for the best quality of living ranks Athens as #77, the lowest ranking of all Western European cities for several years in a row. Barcelona and Madrid scrape in at # 42 and #43 respectively while Paris and London each score 32 and 38 respectively. None of these scores are truly complimentary for the respective cities all with a long tradition of admired urbanism to which NA cities aspire. Better models perhaps may be found elsewhere.

A 2009 review by the Economist of 140 international cities, using other criteria, ranked Athens #64 while Paris was ranked #17, Rome #52  and Helsinki   #7 . Interviewed on the occasion of these ratings a university planning professor said: “…. the urban environment of Athens, although relatively new, is characterized by low quality, and high densities not only of residential building but also of offices, schools and hospitals. There is a big disproportion in the provision of public space and open green space between West European metropolitan areas and Athens”

These rankings and the previous statistics raise questions about urban progress with unforeseen consequences, and about the elements of good urbanism that satisfies the needs of the city’s residents for health, safety and delight.

Conclusions  

It appears that every single urbanist approach, which Athens exemplifies, fails to deliver anticipated results.  This challenges current theoretical assumptions and design directives. Clearly, there are elements in the Athenian version of natural urbanism that produce unwelcome outcomes; they should be clearly identified as warning signs to planners.

The above statistics and descriptions paint a grim picture of Athens as a city far from satisfactory, let alone enjoyable, for its inhabitants. It is also unfavourable to the environment. It would seem that the pinnacle of urbanism that achieved the eradication of suburbs came at a substantial quality of life and environmental costs. 

Dysfunctional cases in any discipline usually trigger deep insights by demanding explanation. In that vein, Athens, a case of dysfunctional urbanism, offers a true laboratory for testing assumptions, principles and theories toward a more robust model of an urbane city.

We can begin unravelling the intrigue, with a set of radical, disquieting questions that might set a valid research agenda:

  • Is the urban malaise attributed to the suburbs misplaced and their eradication the wrong prescription?
  • If Athens’ problems are not attributable to its high level of urbanism, what lies behind them?
  • If urbanism did not fix Athens’ suburban symptoms, what will fix its current urban malaise of congestion, noise, lack of green, sunlight,  declining transit share, little walking and no bicycling?
  • Do urbanist prescriptions have thresholds beyond which they may have negative repercussions?
  • If the Athenian version of urbanism is unworkable, what is a “good” model to emulate? what would its characteristics be?
  • Is there a prospect of recuperation from this advanced dysfunctional stage and in what direction?

These and other questions, arising from a contemporary example of a city without suburbs, could open up a quest for an urbanism free of undesirable consequences. If not the Athenian urbanism, what kind?

Fanis Grammenos, Urban Pattern Associates  

NOTE: This article first appeared in www.planetizen.com in February 2011.

References 

  1. WS Atkins Transport Planning: European Best Practice in the Delivery of Integrated Transport, November 2001
  2. Yorgos K. VOUKAS, 2001, Personal Transportation in Athens. Master’s Thesis, Lund University, Sweden
  3. http://livingingreece.gr/2008/06/20/athens-greece-quality-of-living/   
  4. Pierre Filion  et Al : Canada-US Metropolitan Density Patterns: Zonal Convergence and Divergence
  5. Georgios Sarigiannis , 2000, Athens 1830 – 2000 :  Evolution -Planning – Transportation ( in Greek)

New Urban Epicurean Enterprise

Nested in the woods, L’ Ore du Bois sits  at the  edge of a  village, a 20 minute drive from the nearest Metro urban centre of a million people. A coveted place for epicurean eating, it serves three sittings per evening to about 60 tables. The natural surroundings are charming with the changing seasons and the interior ambiance recreates the nostalgic warmth of a 19th century country house.

An Epicurian Restaurant Nested in the Woods

There is ample parking for all the guests, mostly from the affluent city, hidden behind trees , invisible from the road and with a gravel pad and natural drainage.  The owners even cultivate  spices and vegetables for the meals.

Outstanding  fresh food,  in a perfect setting, sensitive to nature, with exemplar design sensibility this seems a model for a successful, small, independent enterprise, that produces valued diversity and unique experiences , except ……………..

This eclectic, epicurean living is possible only in our New Urban world. No entrepreneur would have conceived of a restaurant in the woods 30 km from town in the urban, horse-dependent 19th century.   The increased and distributed wealth and its wheels of our culture make it possible; copies of this business model abound.

Exclusive traffic magnets like this range in scale from a restaurant to an amusement park, to a zoo, to a casino and to Disney World. They attract people from either a metro region,  a regional district of cities and towns or continental regions of states and provinces.

Large enterprises are considered job and wealth generating ventures benefiting the economy in general and increase local revenues and therefore not only above criticism but commendable. Small enterprises are characterized as  anti-urban.  They are simply New Urban because they thrive in the contemporay urban environment of afluence and mobility.

At home with the car

 

The old mews, now converted to coveted, quiet residential courts was one of planners’ answers to accommodating horse and carriage; what are our solutions for the “horseless carriage”?

Space for the car has been an irritation on the developers and planner’s minds for good reasons. It uses up valuable land; it adds to the house price; it affects the street appeal and can affect the environment. It is not an easy puzzle to solve; luckily, others have been there before.

Let’s try and trace previous solutions and their logic and adapt them to suit a new neighbourhood plan. Start by accepting that cars are vital, valuable possessions and it costs to own them, keep them and to use them. Many tradesmen earn their livelihood by being on the move. Controlling the costs of its home and its impacts is the true task.

Garage within house envelope and unobtrusive

                                 Control starts with optimizing the land it takes to house the car.  Building compact pays off because more can be done with the same land parcel. This means building up not out to accommodate the car and sticking with regular house shapes. Tuck the garage below habitable space; there are plenty of examples of how this can be done well.  Putting the car under living space has other advantages also. It reduces excavation and foundation costs and, importantly, it squeezes the footprint of the house. Lower footprint means more space for rainwater absorption, a “green” advantage that can be a selling point.

A back lane turns into a greenway path

                                As the price of land goes up, lot sizes come down and housing for the car becomes harder. When the lot frontage reaches 33, 30, 25 and 20 feet and, sometimes, 16feet for townhouses it seems almost next to impossible to come up with an effective, good-looking solution.

A seemingly easy solution is to use back lanes but it comes with heavy penalties: more infrastructure to build and maintain; the garage requires a separate structure with its own foundation;   and the lane may add a maintenance cost, as some cities refuse to clear snow in lanes. It also adds to the total house footprint. From a buyer perspective, it takes away precious yard flower-and-spices space and may add discomfort, particularly in the winter, in reaching the house door.  Finally, the unsupervised lane could turn into a hiding place and also an untidy spot. Disputes may arise about cleanliness.

More effective, advantageous solutions do exist. One, by manipulating the lot size, we can increase its width and reduce its depth keeping the same lot area but now having the advantage of the critical extra feet at the front of the house which permit a proper entrance and a garage door in balanced sizes. For example, a 16-foot townhouse bay would become 20 but the lot only 80 feet long. The increase in frontage width makes the house plan more efficient: fewer corridors and wider rooms.

The same logic works for narrow semis and even singles; a better front and a better floor plan. In all these cases and when there is sufficient frontage, keep the garage from protruding in the front yard. For every foot of protrusion an equal amount of usable, precious backyard is lost.

The next solution for narrow frontage lots is to park the car in the basement. No front or rear garages no driveways by the house entrance no asphalted lanes; only a bit of extra foundation work that comes with an advantage – a large deck overlooking the back yard. Units in this solution share a covered driveway and each has a private lockable garage under it. And because it hides all signs of the car, driveways, garage doors and garages, it gives a greener look to the street and increases the permeability of the site. (see Bois Franc). A variation on this theme is individual access to the half-sunk basement from the front; a common solution in renovated townhouses and sometimes in new. To get a spot for a tree, combine two driveways at the sidewalk.

Invisible individual parking under a deck

                                 A newcomer to the range solutions, suits wide, large houses that sit on a constrained lot. The “entry court” option uses the garage to create the “court” and makes it part of the front fence and gate. Set astride the property line each of two  garages face one side and take only ten feet from the lot space leaving about thirty or so for the  paved and landscaped court.

A natural complement to all solutions is the range of new materials for driveways and walkways that allow water infiltration and in some cases even grass to grow through them.

With this range of solutions, you can be at home with the car.

Note: This article first appeared in the Canadian Home Builder Magazine.

Supermodel Sirens on “Sanctuary” Island

  

In a recent  article “Can you see a pattern?”, Witold Rybczynski  praised the genius of C. Alexander and deplored the fact his great work is absent from  architecture and planning schools curricula.  Instead, he grieved, schools are busy with obscure academic wanderings e.g. deconstructivism or other mind-numbing –isms. The rigour and depth of research, such as Alexander’s and a preoccupation to translate it into applicable advice are given up in preference for abstruse esoteric theorizing or preaching. Though he created a large following, he fathered no –ism, simply a seminal book. Neither did he profess that the “Patterns” would be essential in solving the energy crunch, social disparities, alienation, ugliness, crime and other man-made city problems.

While absent in academia, Alexander still exerts influence in these two fields. Many practitioners admit to having his Pattern Language “handy on the desk as a constant reference”. On the research side, his disciples, collaborators and many followers, among whom I humbly place myself, continue the exploration. A major contribution is the latest paper by a team of four (Michael Mehaffy, Sergio Porta, Yodan Rofe and Nikos Salingaros) which advances Alexander’s work to its logical next stage:  a general circulation network model that subsumes and integrates many preceding detailed patterns; a super-model, an Alexandrian SimCity one might say.

 

Figure 1. Organic networks obey fractal laws of organization and appear simultaneously orderly and irregular

                                                                                                                                      The paper touches on many current topical and contested issues and settles a few. As I understood it, the paper:

  • Pronounces the social/spatial doctrine of the “Neighbourhood Unit” dead by research and declares “neighbourhood” and “community” terra non-grata for determinism. It posits that one cannot “design” a neighbourhood or a community; each emerges where and when conditions are conducive and they take shape within or in spite and across “preordained” boundaries. This finding may surprise some who write about “architecture of community” or others who circumscribe fictional “villages”, “towns” and neighbourhoods in the flux of the urban archipelago.
  • Restores the primacy of traffic in creating wealth and “society”.  The surprise here is “society”. Planners have reckoned traffic as the Jekyll and Hyde of contemporary cities. Welcomed and sought after for the goods it bestows, despised and incriminated for its savage hunger for space and speed.  But while it can erode city space and increase risk, it can also irrigate social growth by means connecting goods, ideas and people. Interestingly, an old Greek term for a wide street is “leophoros”, a people-bringer, a social super-collider.
  • Reinforces and adopts the “sanctuary” cell as an organizing unit. It finds that a cellular structure evolves just as naturally in city districts as in organisms. The new cells are selectively permeable and averse to through traffic and thus become sanctuaries for home-based activities. Were possible, their tranquility and delight are enhanced by a focal green space.
  • Accepts “hierarchy” as an underlying structuring principle that is common to fractal natural systems such as veins, brains, and trees, among many. Hierarchy of lengths and widths of connectors influences which will become Main Street, side street, footpath or dead-end.
  • Reiterates and strengthens the 400 m rule, persistent in foot-based settlements and surfacing in most planning documents. This time it becomes the inviolable measure of a well-functioning network. It sets up the scale of human comfort that is intended to permeate neigbourhoods and districts.
  • Repositions firmly the public uses (nuclei) where they have spontaneously emerged throughout history: at the crossroads of main roads and their extensions, not in fictional “centres”. The “Emergent Neighbourhood” model reconstructs a sound foundation for their location.

Why bother with a supermodel?  The same unassailable rationale that stood behind creating the master-compendium of 260 “patterns” applies equally well to creating one that summarizes many. One step up in the organization ladder: from genomes to organs and to a full organism. 

Another good reason is that it might help refocus the planning discourse where Alexander placed it in the 70s: on the rational analysis of conflicts and their physical resolution.

A third ground is the common aspiration of all disciplines for a unified theory that explains the whole gamut of observable phenomena; a fundamental belief that order underlies the apparent chaos.

 

Fig. 2. Two earlier circulation network models (at different scales) both denigrated but not replaced.

                                                                                                                                                                                                                                    Finally, one very practical ground. Ever since the denigration of the transportation network models set out by NCUT (1958) and ITE (1984), an intellectual vacuum was created that was soon filled with vague notions of the “organic” network, the “village” image and the “small town” perfection or simply “the grid”. Organic networks are fascinating to look at but hardly applicable to cities directly. The same applies to images of villages and towns. The growth and ultimate form of each of these networks emerges from a codified set of relationships conducive to survival. A model that draws on and expresses contemporary relationships is needed to fill the void.

With this newcomer, there are now three contemporary alluring supermodels that have more similarities than differences: The “Urban Network”, the “Fused Grid” and now the “Emergent Neighbourhood”; “contemporary”, because they are all born of the dynamics and tensions of a young and unprecedented era – ours. They all arrive at similar organizing principles even though each starts from a distinct mix of premises. 

The paper promises more research to supplement the logic of its propositions. In addition the authors may look at how to reintegrate explicitly Alexander’s previous neighbourhood and district related patterns. Moreover, no large scale pattern would be complete without incorporating the intercity connectors and their relationship to the local network, a challenge that has yet to be taken up. The authors seem set to do hard-nosed analyses of traffic, accessibility, mobility and economic efficiency to strengthen the model so that it can supplant current –isms and be applied.  

With three “patterns” on the table there is little excuse to handcraft picturesque solutions for a problem that has deep organizing dynamics. Centered on these models a new research focus may even give birth to a discipline – URBANOMICS – that deals with “laws” that drive and shape urban development.

 The continuing absence of fundamental laws has left the field dependent on images that inevitably generate endless and tiresome imitation. The proposed model fills a gap and may rekindle not only elemental thinking but also diversity.

Descriptions of the latest and previous models can be found here:

http://www.palgrave-journals.com/udi/journal/v15/n1/abs/udi200926a.html

http://www.calthorpe.com/publications/urban-network-new-framework-growth

This article was first published in Planetizen  www.planetizen.com

A Fused Grid Neighbourhood in Construction

A new Calgary neighbourhood shows the features of a good, Fused Grid  neighbourhood  

In Calgary, Alberta work has begun on a new 64 hectare subdivision that will put leading edge urban planning walkability principles into practice.  Named Saddlestone, the new community uses the Fused Grid model.  

http://www.genesisland.com/land/saddlestone/community-map.html 

The Fused Grid model is a new way of arranging streets and open spaces to allow for a high level of pedestrian connectivity, while limiting the amount of automobile through-traffic within residential areas. It blends the best features of the gridiron system common in traditional urban areas and the looping streets and cul-de-sacs of more conventionally designed suburban areas. It does this by shifting most of the traffic to continuous through-traffic roads around the perimeter of the neighbourhood, while making streets discontinuous within the neighbourhoods.   

land use concept
Land Use Concept of the 160 acre neighbourhood

The key in making this arrangement highly walkable is the use of strategically placed footpaths, linear parks and open spaces to ensure a continuous pedestrian network within the neighbourhood. This results in slowing traffic around residential areas while leaving pedestrian flow uninterrupted, with direct, efficient and pleasant walking routes to parks, transit and amenities.  

The integration of the Fused Grid model into plans for Saddleton began in 2004, when the developer, Genesis Land Developments, began collaborating with the CMHC on the creation of a site plan that incorporated the model’s key principles. Municipal approval for the plan was given in 2008, at the conclusion of a process that included meetings with city officials and revisions to the initial plan, submission of a full development application, a public open house, a presentation to the Calgary Planning Commission and a public hearing of City Council.  

Saddleton’s application of the Fused Grid model is a significant step forward for this planning approach. It will demonstrate the model and its benefits in a concrete fashion and will be of great interest to municipalities, developers, home buyers, active living/transportation advocates and others as the new community takes shape.  

Walking didtance to parks

Increasing pedestrian connectivity while limiting vehicle connectivity within neighbourhoods, as the Fused Grid does, has been shown to improve rates of walking and physical activity for residents. A research study compared rates of walking in neighbourhoods with different levels of pedestrian and vehicle connectivity, including neighbourhoods with and without traffic calming measures, such as “diagonal diverters” and streets closed to cars but not to pedestrians and cyclists.  

The research found the highest rates of trips by foot (18 per cent) in areas where pedestrian connectivity was higher than vehicle connectivity. This compared with 14 per cent for areas with high levels of both pedestrian and vehicle connectivity and 10 per cent for areas with low pedestrian connectivity.   

Extesnsive network of paths add to the street connectivity

  The Fused Grid’s positive impact on walking is not at the expense of efficient traffic flow— a traffic simulation study showed that the Fused Grid model would allow an efficient flow of traffic and is superior to several other street layouts. Both pedestrian comfort and car movement are accommodated with sizeable reductions in the risk of collisions. Most street intersections on the site are 3-way which according to recent  research studies are the safest. 

In summary, neighbourhoods like Saddleton could enhance active living, reduce accidents and lower harmful car emissions. Moreover, they would create a milieu that blends nature, a restorative feature, in an urban setting.  

FUSED GRID: Open spaces with a triple function: recreation, pathway node and rainwater filtration are  part of the site plan:   


Three research highlights provide a quick tour of the ideas behind this new neighbourhood and the Fused Grid planning model:  

Canada Mortgage and Housing Corporation.  Breaking Ground: A Fused Grid Neighbourhood in Calgary. Research Highlight: Socio-economic Series 08-020. December 2008. Available at: www.cmhc.ca  

[ii] Canada Mortgage and Housing Corporation. Giving Pedestrians An Edge — Using Street Layout to Influence Transportation Choice. Research Highlight: Socio-economic Series 08-013. July 2008. Available at: www.cmhc.ca  

[iii] Canadia Mortgage and Housing Commission. Taming the Flow — Better Traffic and Safer Neighbourhoods. Research Highlight: Socio-economic Series 08-012. July 2008. Available at: www.cmhc.ca