Category Archives: Existing City Network Adaptation

the Adaptation of Existing City Network

Bumpy rides a thing of the past, again.

          

Does a driver exist who actually likes speed bumps and humps?  If not, what are these road skin inflammations doing at mid-block or at intersections?

 It seems ironic that we paved bumpy, dirt roads to ease our trip and then, some half a century later, we purposely create bumps that turn it unpleasant. It’s also strange that at intersections, our three natural options for continuing on are often curtailed to two or just one; surprised and stuck with no choice! These changes sure look like embarrassing afterthoughts.

Bollards turn a 4-way junction into 3-way. Landscaping offers a relief.

We normally do renovations to systems that no longer meet requirements which stem from a new understanding of health, safety or efficiency concerns. We change steep stairs to prevent falls or upgrade an electrical service to power more home appliances.

But why remodel streets? After all they have functioned for hundreds of years.  True, but in the last hundred much has changed in them that slipped in unnoticed.

First, speed on the streets increased from a leisurely 5 km/hr to a hurried 30 and up to fifty; a six-fold increase at least. Then the size of their occupants increased from about a four square feet, a man’s footprint, to a driver’s of 200 square feet; a 50-fold increase. In addition, noise levels climbed from the human chatter of 50 decibels to the truck and motorcycle clatter of 75 decibels, more than a 100-fold increase in ear pressure.  And finally, a subtle existential angst pervades the streets; a wolf has found its way into a sheep’s pen; risk is lurking at every corner. These entirely new urban conditions call for remodelling; and remodelling we did and it will be going on for a while.

Take the cross intersection for example, a relic from the past. When people come to it, it’s a meeting place, but when cars reach it, it turns into a conflict zone. There are 32 ways that cars can collide in it. Unless the intersection is signed or signalized, every driver naturally believes in his right to act and move first.  Stats show that 4-way intersections have much higher frequency of collisions than the 3-way alternative.  The lesson learned, neighbourhoods started to remodel their 4-way junctions. One approach is to close one of the crossing streets at the intersection, promptly turning it into a 3-way.  Bollards, a clump of trees or planters make the closure an attractive feature. The second means is to install a traffic circle in the exact centre of the intersection. From a driver’s perspective, this addition has the effect of turning the crossing point into four virtual3-way junctions; direct forward movement is not an option. As with the closure, the circle can host shrubs, flowers, or a tree improving the street ambiance. Closures and traffic circles are just two of many ways of adapting the old network to the traffic it did not anticipate.

When remodelling or designing neighbourhoods for traffic, two goals are uppermost:  Safety and flow and in that order. 

What can traffic circles do for safety? Seattle’s traffic safety program, starting in the 90s, evaluated the impact of 119 traffic circles on accidents and injuries. It showed a whopping 90 percent reduction in both. And when counting all costs related to accidents, the installation proved convincingly cost effective. Five hundred more installations followed.

 Vancouver did its own renovation and remodelling of certain streets. It included street closures, traffic circles, diverters, curb extensions, and extra traffic signs. A study, that looked at the before and after frequencies of collisions and injuries in the entire district, found that there was a general reduction of accidents by 15 percent and, within neighbourhoods, of about 25 percent.

A small circle, provides a great safety bonus

But do traffic circles improve flow? Surprisingly, yes. Even though drivers slow down to negotiate the circle and other cars, the total network flow performance improves.

The lesson: neighbourhoods can do without the old four way intersections and improve safety to boot. Traffic circles are smarter bumps that cars drive by not over, recapturing the comfort of a smooth drive.

 These renovations bring welcome improvements to an antiquated network system.

New neighbourhoods can use the lessons from these upgrades and provide a safe and well functioning network from the start. The techniques are easy to apply:

a)      Avoid intersections entirely within a neighbourhood; unimaginable but possible.

b)      When junctions are necessary, use the 3-way version

c)      Use turns, not curves or bumps,  to slow down cars

d)      On streets surrounding the neighbourhood use traffic circles at the intersections

With these features in place, bumpy rides can be a thing of the past, again.

Ref: Seattle’s traffic safety program: http://www.usroads.com/journals/rmej/9801/rm980102.htm

 

Old Urbanism to Fused Grid – Montpellier

Old Urbanism to Fused Grid - Montpellier

 

Network Transformation

Montpellier in 2004 took a bold and unprecedented step to turn the entire 800-year old fortified city into a pedestrian realm. It  adapted its inherited organic grid to the car and light rail by applying the Fused Grid model.

 A perimeter road (red) frames an area about 1000 m by 1200 m. Only two feeder roads (blue) serve the distinct district but none goes through.  Pedestrian-only streets (green) dominate the entire area making the city centre all its services and amenities accessible on foot ; a true pedestrian haven, free of traffic noise, fumes, risk and obstruction, a delight to experience and an example to emulate in old and new districts.

Old street networks  accommodated the transport means of the time – foot, hoof and cart. The car, train, tram and truck, because of their need for space and speed, usurped most or all of the street space from the pedestrians over time. The public realm became mostly a car realm. Returning a district to its original state of exclusively pedetrian traffic,  recognizes the nature of the network and its incompatibility with contemporary transport modes.  Learning from this transformation, new districts in cities can combine pedestrian-only streets and paths with streets that serve the car in a network that balances the needs and enjoyment of both – the Fused Grid

Montpellier - Fused GridMontpellier - Fused Grid

Arrested Evolution – A living urban past

Arrested Urban Evolution

It didn’t happen and won’t happen.
People walking these streets will not experience the clutter of evolution that accommodates the car, ever. Car-free means no clutter, no noise, no fumes; a peaceful walk that includes only faces and voices.
These qualities can only be recreated in a Fused Grid neighbourhood (see Wikipedia) where portions of the network is solely for pedestrians.

While many old cities have forcefully adapted to the car, hill and island villages in the meditarean have escaped the need for adaptation because of the chosen site topography. They stand as reminders of what a pedetrian world was like, arduous but peaceful, free of any of the nuissances of motorized transportation.

The two pictures below show steep and stepped streets in wchic not even donkeys can be used for accessing houses; wheeled implement motorized or not are out of the question (and the picture). All movement and transport of goods hapens on foot.

DSCN6224Kea, Greece

Strasbourg – Old urbanism to FusedGrid

Strasbourg - Old urbanism to FusedGrid

Strasbourg, France turned much of the old fortified city into a pedestrian priority realm.
It adapted its inherited organic street network to the car and light rail by applying the Fused Grid model. A perimeter road (red) frames the central district, which is about 800 m wide by 900 m long, the dimensions of a walkable area.  Feeder roads (blue) serve the distinct but do not go through directly, particularly in the North-South direction.  Pedestrian-only streets (green) dominate the area making the city centre all its services and amenities accessible on foot ; a true pedestrian haven, free of traffic noise, fumes, risk and obstruction, a delight to experience and an example to emulate in old and new districts. Photos by Michael Afar

Strasbourg - Old Urbanism to Fused GridStrasbourg - Old Urbanism to Fused Grid

Strasbourg - Old Urbanism to Fused GridStrasbourg - Old Urbanism to Fused Grid

Frankfurt – Old urbanism to Fused Grid

Frankfurt - Old urbanism to Fused Grid

Frankfurt, Germany turned much of the old fortified city into a pedestrian priority realm. It adapted its inherited organic street network to the car and rail by applying the Fused Grid model (see Wikipedia).

A twinned perimeter road (red) frames the central district, which is about 900 m wide by 1500 m long, the dimensions of a walkable area.  Feeder roads (blue) serve the distinct but do not go through directly, particularly in the North-South direction.  Pedestrian-only streets (green) dominate the area making the city centre, all its services and amenities accessible on foot ; a true pedestrian haven, free of traffic noise, fumes, risk and obstruction, a delight to experience and an example to emulate in old and new districts.

The streets below have been returned to their rightful owners, the pedestrians, and thus have re-established the tru meaning of “the public realm”.

Frankfurt- Old Urbanism to Fused GridFrankfurt- Old Urbanism to Fused Grid

New Urbanist Cul-de-sac

New Urbanist Cul-de-sac

A city neighbourhood displays a perfect New Urbanist cul-de-sac:
This 200-foot long street is built at high density, common to the entire neighbourhood.
It is narrow and shared between pedestrians and cars, a common public realm made possible because of its short length and width, the number of cars on it and the absence of through traffic.

At the end, it opens to a path that connects it to the street across (photo on the right) and to all other streets along the path which is set in a delightful green space  of  only 60 feet in width. The same space is used for dog walking, kids’ play, exercising and inevitably socializing. This public realm is free of all nuisance, relaxing and joyful. At both ends of the five minute path walk one finds a bus stop and convenience stores.
This neighbourhood consisting of ten short, rectilinear cul-de-sacs is compact, connected, safe, has a mix of uses, is served by transit and has a delightful public realm.
Urbanism comes in many guises – often in a cul-de-sac.