Transportation Networks Part 1

"The global destruction of cities and countryside, of human cultures and of nature itself, can only be reversed by a global philosophical, technical, cultural, moral and economic project: by an ecological project.

 The city is not the unavoidable result of a society's activities.

 It can only be built and maintained when it represents the goal of individuals, of a society and its institutions.

A city is not an economic accident but a moral project. Forms of production ought no longer to dictate the form of the city; but the form of the city, its organic nature and moral order, must qualify and shape the forms and of production and of exchange."

Léon Krier     

(Photo by Léon Krier)

City Transportation Networks

We will address the transportation issue from a network design point of view first.  Later in this series we will address buildings, which are are more complex, more numerous and offer a greater variety of opportunities for saving energy and combatting global warming.

Even though it ranks third on the list of causes of global warming, that doesn’t mean that it’s impact isn’t significant to a degree that is unsupportable and that to continue on the path we are on isn’t irrational.  The Texas Transportation Institute, which states that “Traffic congestion continues to worsen in American cities of all sizes, creating a $78 billion annual drain on the U.S. economy in the form of 4.2 billion lost hours and 2.9 billion gallons of wasted fuel”. 

Depending on the quality of the crude oil used to produce the gasoline, that means that somewhere between four and fourteen days of the total oil consumption in the U.S. is wasted in traffic congestion.  That doesn’t include the wastage at normal traffic stops, inefficient routing or other fuel wasters. That wasted petrol becomes 25 billion kilos of CO2 dumped into the atmosphere utterly without purpose.

As the U.S. transportation grid, for all of its inefficiencies, is substantially more efficient than many around the world, one thing is abundantly clear: transportation network design is critically important as one of the components to reducing global warming.

For this series we are using a multidimensional approach to viewing transportation networks: fuel efficiency, minimum transit times and psychic satisfaction.  A network that doesn’t satisfy all of these simply isn’t acceptable.

The Congress for the New Urbanism has looked into this and developed this comparison of where we should be and where we are today in terms of design:

Modern Network Design	Conventional Roadway Networks
Highly Connected	Partially Connected
Multimodal	Auto-dependent
Accessible Destinations	Indirect Routes
More Public Streets	Fewer Public Streets
Detailed Streetscapes	Few Streetscape Elements
Welcoming for Pedestrians	Dangerous and Unpleasant for Pedestrians
More Route Choices / Redundant	Fewer Route Choices / Prone to Break Down
Smaller/Narrower Streets	Wider Streets
Finer Grained	Coarser Grained
Lower Speeds but Faster Trip	Higher Speeds but Longer Trips
Focus on Quality of Place	Focus on Flow of Vehicles
Less Delay at Intersections	More Delay at Intersections
Simpler Turns	More Complicated Turns
Supports Activity on Sidewalks   Adjacent to Streets	Sidewalk and Adjacent Activity Subservient to Traffic Flow

It took a deep understanding of the environment in which we immerse ourselves to develop a modern network design and it would be difficult to find anyone who wouldn’t find it appealing.   However, we are living in the world that was defined by cheap oil, self-gratification and community disintegration.  The sunk capital in this world is immense and isn’t going away any time soon.  Immense tracts of arable land have been and are being paved over in greenfield areas even as food scarcity is increasing and costs rising because of resource shortages and climate change.  It is clear that we must work within the existing urban and suburban road networks to create the environment of the future which means infilling, repurposing and redesigning.  It is not going to be inexpensive.

Before proceeding with looking at that in the next posting, let’s put a little flesh around the bones that the CNU has provided.

Highly Connected vs. Partially Connected networks.

Highly connected networks provide lots of redundancy for getting from point A to point B and tend to spread out the traffic load.  Partially connected networks, on the other hand, push traffic onto a few routes which are therefore more heavily trafficked.  A fully connected network would be the most efficient for moving traffic around, but it would also be the most expensive, so the highly connected network can be viewed as a trade-off between a partially connected network and a fully connected one, leaving room for effective design not only for traffic flow but also for providing an aesthetically pleasing streetscape.

A simplified version of the conceptually difference is supplied by CNU:

    Driving only, Partially connected Network           Walkable highly connected network

Same houses, same school.  If it were your house and your school, which would you feel more comfortable having your child walk to alone?  Which network is more likely to provide the opportunity for interesting streetscapes?  Which one conserves energy?  The answer is clear.

What is also clear is that making the neighborhood more walkable and the school more accessible would not be expensive and this is the kind of retrofitting we need to do for our communities: 

Livability on the cheap - reconnecting using pedestrian/bicycle ways, short connectors & easements.

Because we cannot simply raze existing estates and developments, it is necessary to find ways to make them work in an increasingly resource-constrained world.  The CNU has some general prescriptions:

• Connectivity Enhancements: These projects increase the number of intersections/square mile by removing gaps in the network.
• Road Diets: These projects reduce the number of lanes or lane widths to accommodate more pedestrian capacity and/or improve vehicular speed on the roadway.
• Intersection Diets: These projects add pedestrian bulb outs and remove right hand turn lanes so that the crossing distance for pedestrians is reduced.
• Decrease Block Size: These projects add streets to large, underutilized projects, like greyfields and brownfields.
• Sidewalk enhancements: These projects increase sidewalk width and/or improve pedestrian amenities.
• Two-way conversions: Projects that replace one-way streets with two-way streets.

Context Sensitive Design Approach outlined in the Institute of Transportation Engineer’s 
Context Sensitive Solutions in Designing Major Urban Thoroughfares for Walkable 
Communities. 
 
Constrained resources make it necessary to intelligently retrofit communities, both suburban and urban, to reduce energy and material consumption.  Intelligent reordering of priorities steers us away from the mere acquisition of more and more goods to the enjoyment of what we have and what is around us.  Communities need to rebuild themselves for this new priority at the same time that they prepare for the resource crunch that is beginning to be felt.