In an earlier article, Beloved and Abandoned, we presented the grid plan, using Portland’s layout, as a historic relic perhaps deserving of attention but clearly unfit for replication in contemporary settings. That, evidently, is not occurring in any case. Several commentators quickly pointed to the supreme legibility of the simple grid as a counterpoint; clearly an indispensible attribute, they said. But is it?

The value of legibility lies in its presumed link to navigation. It is assumed that good legibility makes navigation easier. But does it?  Is a simple, orthogonal geometry aligned with the cardinal directions a necessary condition for easy city navigation? Apparently not, as we shall see.

Though related, the two concepts, navigation and legibility, are quite distinct. One is about an act and the other about a mental construct. “Navigation” and “way-finding” appear interchangeably in architectural and planning literature and they both mean reaching a destination with ease. “Legibility” which originates from text reading, is harder to grasp, but it does relate to a map in the mind, be it a letter, a picture or a configuration of streets. Legibility expresses the ability to project an image and discern its match with what one sees. Navigation as an act could be compared to dancing – a sequence of rhythm-coded steps that is partly or entirely preset and that becomes intuitive.

The first notion to consider in deciphering this puzzle is that navigation, or finding one’s way to a destination, not only predates geometry by millennia, but it is also a basic skill of most sentient, even “non-intelligent,” life. Examples abound from bees to birds to fish and turtles and many more. Closer to home, emotional, and sometimes incredulous, recounting of pets returning from a distant foster home, point to that instinctive ability.

In humans, a few striking examples, first from the non-urban world, show the distinctiveness of the two concepts and the independence of navigation from geometry.

Inuit will trek for many kilometers beyond the base horizon in pursuit of game, often in poor visibility, in what seems an undifferentiated, unremarkable, featureless landscape and, surprisingly to us urbanites, find their way to a destination and back home with astonishing efficiency.  Legibility, understood as a geometric order or map, is entirely irrelevant in this landscape.

Figure 1. The feat of seafaring for thousands of kilometers in the Pacific Ocean without a single navigation aid still astonishes cultural anthropologists and navy captains (image from Wikipedia)

An even more astonishing example comes from Polynesia. For many centuries before they were “discovered” in 1595, the Marquesas inhabitants had ploughed the vast Pacific Ocean in stone-age-tool-crafted open catamarans to trade with and settle in other distant pacific islands. The crew of ten included a captain and a “wayfinder”, two very distinct roles (the wayfinder does not sleep!). Not a single navigational aid existed on board. These seafaring traders and settlers were able to regularly reach distant ports well beyond the visible horizon, often thousands of kilometers away, with accuracy and efficiency that surpassed by far the skills of fully equipped European sailors.  A great captain, Magellan, for example, sailing west from Cape Horn, missed the Marquesas and other pacific archipelagos to land, months later, with a malnourished and decimated crew, on Philippines.  The Marquesas wayfinder “knew” his directions with infallible precision. Nothing could be less “legible” and more disorienting than a vast, featureless ocean during weeks of sailing.  Evidently in this case, legibility, as a geometric construct, has little to do with navigation.

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 Figure 2: A typical medieval city street network within a perimeter wall, now a peripheral arterial. Visitors get easily lost in the maze, but not its residents.

From the urban world, examples also show that navigation does not depend on legibility.  Most visitors describe Arab cities such as Fez, and Marrakech or Medieval cites such as Vienna and Martina Franca (Fig.2) or Asian cities such as old Tokyo and Mumbai, as mazes, impossible to navigate even with a map in hand. In each case, the street pattern lacks clear geometry, has no uniformity or repetition, is rarely rectilinear and seldom abides with cardinal directions. Yet for many centuries, the residents of these cities thought nothing of navigating through their streets. Even more surprising, these same labyrinthine streets had no names and house numbers, yet posed no difficulty to reaching destinations.  Intensifying the surprise, are the cases of planned Roman cities with a highly legible orthogonal grid that were transformed into maze-like patterns by their subsequent occupants as if legibility was undesirable.

Figure 3. Old Vienna’s street network is typical of many medieval cities: irregular, idiosyncratic, varied bock sizes and shapes with multiple orientations,  maze-like. (green indicates pedestrian-only  streets) Giving verbal instructions to a destination could be an insurmountable challenge; following them, an impossibility.

If navigation was not an issue in these early pre-urban, non-urban and urban conditions, then the introduction of a simple geometric arrangement of straight streets and repetitive blocks would seem unnecessary for that purpose. In fact, Aristotle, long after Hippodamus drew the famous grid plan of Miletus, argued against his configuration and in favour of the old, “organic”, labyrinthine pattern on the grounds of defence, as did Alberti 1,500 years later. Camillo Sitte made the same case on aesthetic grounds, entirely unconcerned about legibility, having lived in Vienna, (figure 3) a medieval city, and grown to admire many other similar cities, with irregular street patterns.

These examples show clearly that humans on foot, on horses, carts and in boats have been able to find their way to a destination in natural, non-urban and in urban environments unaided by geometry and printed maps. The one presumed outstanding feature of the simple grid, legibility, proves to be unnecessary for navigation and simply an after the fact attribution by post-Guttenberg humans looking at maps.

Fanis Grammenos is a principal of Urban Pattern Associates and was a Senior Researcher at Canada Mortgage and Housing Corporation for over 20 years. He focused on housing affordability, building adaptability, municipal regulations, sustainable development and, recently, on street network patterns. Prior to that he was a housing developer. He holds a degree in Architecture from the U of Waterloo.

A shocking piece of news recently brought home the formidable potency of energy: over 300 million people in India were left without electricity, all of Canada ten times; chaos ensued. Factories, offices, hospitals, and traffic came to an abrupt and apocalyptic standstill.  The engines of the economy, cities, were silenced.  Losing power to such epic proportions has never been the case in the past and for good reasons.

Up to a century ago, in 1850, men and animals supplied 94% of the world’s energy and 5% came from fossil fuels; a ratio that lasted for millennia; no power interruptions in that scenario. But by 1950, a mere century later, the numbers were reversed: 93% of energy came from fossil fuels and 6% from people and animals. And much of the fossil fuel burned to supply the electricity grid which provides power to 75% of the world’s houses, offices, factories etc. Astonishing, unimaginable things happened in that century and the years that followed and, reportedly, more are in store. About 90% of all inventions since the Promethean fire emerged in these last 150 years.  Why so?

What lies behind this enormous creativity? Ultimately, energy. As more hands are displaced by machines, more brains can switch to nurturing ideas. But a second and equally powerful lever to this creative surge is cities: apparently, the bigger they get the more innovation they generate: doubling a city’s size increases its creativity by 15%. Several cities have doubled a number of times in the 20^th century producing a compounding effect.  Cities become beehives of creativity  because they connect people. As different brains interact, more synapses fire, each leading to yet another potential innovation or enterprise. A new tool in the hands of others finds uses unforeseen by its inventor; and the spiral grows exponentially. 

Connectivity

The storyline of connectivity between people traces the path of transportation which shapes the city and determines its size. When human and animal power provided all transport, making a connection meant a trip on foot or hoof and a face to face encounter. News spread at walking speed of 5 km/hr; a slow and often arduous process. In that era most cities reached a population around 30,000 people and a size of about 20 minute walk across. News emanated and propagated from the barber shop, the communal water spring, the pub and later, when coffee become common, the coffee shop.  The circle of interaction was small and the ideas local; inventions were also mostly local and stayed local for generations. When the coal-fired steam engine came on board and followed by the electric motor, cities changed dramatically.

Steam-engine trains and electric trams boosted city size at least ten times and now news and ideas  could be had from places weeks away on foot, in just a day; a double benefit for creativity.  Still, relatives, friends and businesses could only talk to one another by letter; long trips were unaffordable for most.  But the beehive was now much larger, more people interacting and the speed of inventions started to accelerate to the point where a US Patents Office director would declare around 1900s “all that could have been invented has been invented”. The news transmission tower was still at a street corner in the pub or coffee shop.  All of that changed when electrical wires became the highway of communication with the invention of the telegraph and then the telephone, radio and television. 

Overnight the creative “city” was as big as the reach of the telephone line or of the radio signal, which had no practical limits.  Important news about discoveries, opportunities and people came out of speakers or screens.  The barber shop, pub and coffee shop talk was demoted to trivial chit-chat, gossip; little gain to be had from it.  The transmission hub moved to a secluded room someplace no one knew; it didn’t matter.  Electricity made connectivity possible without travel by using wires or airwaves; without travel and at the speed of light!

Not only communication was freed of travel, it was soon freed of filtering, control and reach. With the internet and the cell phone everyone is a hub and a receiver of ideas at the same time.  A video story by anybody can reach a million people or more; at least twenty times the foot and hoof city population.  While you teach a trick to someone on line you can learn another from someone else. Anyone’s ideas can “infect” countless unfamiliar people. City creativity was given another rocket booster.

From walking down to the corner to get news and share ideas to being virtually at every corner of the globe without leaving your living room, connectivity has traveled a long way in a hundred years, thanks to the power of electricity. Power is key to a better future.

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 19^th 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 18^th and 19^th 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.

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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