Traffic Congestion and Greenhouse Gases

Matthew Barth and Kanok Boriboonsomsin

Surface transportation in the United States is a large source of greenhouse gas emissions, and therefore a large contributor to global climate change. Roughly a third of America’s carbon dioxide (CO2) emissions come from moving people or goods, and 80 percent of these emissions are from cars and trucks. To reduce CO2 emissions from the transportation sector, policy makers are primarily pushing for more efficient vehicles, alternative fuels, and reducing vehicle miles traveled (VMT). Those who promote vehicle improvements have focused on building lighter and smaller vehicles (while maintaining safety), improving powertrain efficiency, and introducing alternative technologies such as hybrid and fuel cell vehicles. Alternative fuel possibilities include many low-carbon options such as biofuels and synthetic fuels.

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2017-05-26T23:34:03+00:00Categories: ACCESS 35, Fall 2009|Tags: , |

Moving Los Angeles

Paul Sorensen

People often complain about traffic in Los Angeles, and with good reason. The Texas Transportation Institute publishes annual traffic statistics for metropolitan areas across the United States, and the greater Los Angeles region routinely tops the list for such measures as total congestion delays and congestion delays per peak-period traveler. Against this backdrop, RAND was recently asked to evaluate and recommend near-term strategies that could meaningfully reduce LA’s traffic within a period of five years or less. Note that this timeframe precludes land use policies, which take longer to bear fruit, and major infrastructure investments. In addressing this question, we found it helpful (a) to review general insights from the transportation literature on the causes and potential cures for traffic congestion, and (b) to diagnose the specific local conditions that contribute to the notoriously severe congestion in Los Angeles.

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Transportation Infrastructure And Sustainable Development: New Planning Approaches For Urban Growth

Marlon G. Boarnet

As California's population expands to fifty million people over the next two decades, urban infrastructure will be under immense pressure. Partly in anticipation of growth, and partly to catch up after years of neglected investment, in 2006 California voters approved bond measures for transportation, affordable housing, education, disaster preparedness, flood prevention, and water projects. Most experts expect that even more funding will be needed to meet future needs. How can these funds best be spent to accommodate growth and avoid stressing California’s environmental, fiscal, and social resources? In particular, how can we use the next round of transportation investment to help us plan for a more sustainable future?

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For Whom The Road Tolls: The Politics Of Congestion Pricing

David King, Michael Manville, and Donald Shoup

It is almost universally acknowledged among transportation planners that congestion pricing is the best way, and perhaps the only way, to significantly reduce urban traffic congestion. Politically, however, congestion pricing has always been a tough sell. Most drivers don’t want to pay for roads that are currently free, and most elected officials—aware that drivers are voters—don’t support congestion pricing.

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Learning From Mel

Jonathan Richmond

I first encountered Mel Webber during a brief stay at Berkeley. I had left MIT with a trail of debt and unwisely registered for a PhD at Berkeley with only partial financial aid. Rather than worry about the unpaid rent at International House piling up on top of the five months of unpaid dorm rent I had left at MIT, I became utterly absorbed in the two most astonishing courses I have taken anywhere. One was taught by C. West Churchman, the other by Mel Webber (very ably assisted by Karen Christensen).

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What We’ve Learned About Highway Congestion

Pravin Varaiya

There are 26,000 SENSORS buried under the pavements of California freeways. Every thirty seconds, those sensors send data to our computers here in Berkeley. The data tell us about the number of cars driving on that freeway and their speed at that time. We also collect, process, and store data about collisions and other incidents. This database, PeMS (Performance Monitoring System), is now by far the most comprehensive source of information about California highways. Today it stores four trillion bytes of information, which are available online at We’ve already learned quite a lot from all those data. For example, we’ve found the error in the old belief that an average speed of 40 to 45 mph maximizes traffic capacity; we now know for a fact that maximum capacity occurs at around 60 mph. And we’ve been surprised to discover that some HOV lanes may have the perverse effect of actually adding to congestion.

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Why Traffic Congestion Is Here To Stay…And Will Get Worse

Anthony Downs

Everyone hates traffic congestion. But despite all attempted remedies, it keeps getting worse. Why don’t they do something about it? The answer: because rising traffic congestion is an inescapable condition in all large and growing metropolitan areas across the world, from Los Angeles to Tokyo, from Cairo to São Paulo. Peak-hour traffic congestion is a result of the way modern societies operate, and of residents’ habits that cause them to overload roads and transit systems every day.

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Are Induced-Travel Studies Inducing Bad Investments?

Robert Cervero

Mark Hansen's 1995 ACCESS article presented compelling evidence on induced travel demand. Titled “Do New Highways Generate Traffic?” it drew on eighteen years’ worth of data for fourteen California metropolitan areas and concluded that added road capacity unleashes new travel. The article showed that added trips quickly fill up an improved roadway, bringing it back to its original congested condition. On average, Hansen found, every ten percent increase in road capacity spurred a nine percent increase in traffic volumes within three or four years. That is, around nine-tenths of added road capacity was absorbed by new trips.

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