May 28, 2015

Do we need more and bigger roads?

Some recommended reading from Michael Alexander and others, from the Rocky Mountain Institute.  Here’s a very abridged version.


Does America’s Transportation Future Really Need More and Bigger Roads?


The only argument during the debate (in Congress) last summer was for more roads. If we assume we’ll drive tomorrow the same way we drive today then as U.S. population grows, everyone will buy cars and drive, causing more congestion. To reduce congestion, the argument goes, we need to build more and bigger and wider roads.

Yet several studies debunk that last notion. While adding road capacity temporarily reduces congestion, the capacity quickly fills up again. But, what about the first part of the argument: does an increasing U.S. population necessarily mean more cars and more driving?…

U.S. annual VMT (3 trillion miles averaging out to roughly 14,000 VMT per licensed driver) has leveled off since 2005, with VMT per person decreasing every year. This trend alone points to reconsidering the basic assumptions of this debate.

If these four solutions can further reduce VMT significantly, then we won’t need more roads or more drilling and oil:



Since daily activities make up more than 75 percent of trips in the U.S., living in a walkable, mixed-use neighborhood can dramatically transform mobility, eliminating most driving needs. A comprehensiveVictoria Transport Policy Institute study found it could reduce residents’ VMT up to 20 percent.



Car sharing has already expanded rapidly from 50,000 to nearly 1.5 million U.S. members between 2004 and 2014. And this growth reduces vehicle ownership—every car-share vehicle eliminates 9–13 personal vehicles, with users selling their car or deferring buying one—and reduces total number of vehicles on the road by using cars that are on the road more efficiently via higher utilization rates. … More-efficient and reduced trip-making combined with lower vehicle ownership points to 27–44 percent fewer VMT for car-share users.



Smart parking transforms driving in two ways. First, individual trips are more efficient, with cruising for parking eliminated. … Second, as cruising vehicles are removed from the road, congestion eases for cars traveling through. And the collected data on parking usage combined with smart growth means cities can reduce parking requirements and repurpose existing parking.



Self-driving vehicles are defined by level. Levels 1–2 (adaptive cruise control, lane change assist, collision avoidance) require full driver engagement and are available on current vehicle models. For levels 3–4, the car drives itself with minimal driver intervention. Connected refers to vehicle-to-vehicle and vehicle-to-infrastructure communications (V2X): cars talk to other cars, dynamically reroute around traffic, and “call ahead” to traffic signals to avoid sitting at empty intersections.

First, some 90 percent of crashes are caused by human error and these could be nearly eliminated by self-driving cars, saving thousands of lives. As a secondary benefit, crash-related congestion—accounting for approximately 25 percent of congestion events—would be avoided.

Second, recurring stop-and-go traffic (think rush hour) could be eased through platooning/highway driving with reduced headway, dynamic rerouting, and traffic flow smoothing. Self-driving vehicles can thus double to quadruple highway capacity without expanding the highway, making for smoother, faster trips—although this will require significant market penetration.



These solutions reduce VMT 15 percent by 2040, stopping VMT growth at 2030 levels (using the U.S. Energy Information Administration’s projections as the baseline even though these projections—that VMT will continue to increase despite a decade of flat growth—are generally poor at predicting future traffic trends)..

In the accelerated case, where infrastructure spending focuses not on building more roads but enabling these solutions, VMT growth stalls by 2020 and then decreases.



Imagine taking those savings from not building new roads and instead deploying sensors and software to enable a smarter, more-efficient transportation system.

A major shift is under way, changing the way we will travel over the next 25 years, and the debate needs to shift with it. We should be talking more about maintaining the roads we have and using them (and the vehicles on them) better, instead of how to fund our steady march to more paved land.


UPDATE: From Strong Towns

Last Friday a federal district court ruled in favor of 1000 Friends of Wisconsin in a case they brought against both the US and Wisconsin departments of transportation. At issue was a proposed highway expansion and a set of bogus traffic projections used to justify it. The court said, in essence, that if the DOT is going to project a huge increase in traffic while population and actual traffic counts are dropping, they need to show how they came up with that.

This decision has huge implications. Together we’ve long battled the standard DOT approach of continual highway expansion justified through faulty projection methods. This decision is a really important pushback.

Some links for you:

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