Some folks believe that the only solution to the traffic Armageddon that they slog through every day (the WORST traffic ever!) is to build more lanes. Or another exit and entry point into Alameda. Or just stop building all together. Somehow these three things separately or together will magically make what should be a 30 minute commute even in the best circumstances, a 20 minute or less commute. According to City Lab, Caltrans, the people in charge of building extra capacity, recently linked to a report that found that adding more capacity only exacerbates the problem of traffic. From the City Lab article first:
The brief, titled “Increasing Highway Capacity Unlikely to Relieve Traffic Congestion,” was compiled by UC-Davis scholar Susan Handy. Here are the highlights:
- There’s high-quality evidence for induced demand. All the studies reviewed by Handy used time-series data, “sophisticated econometric techniques,” and controlled for outside variables such as population growth and transit service.
- More roads means more traffic in both the short- and long-term. Adding 10 percent more road capacity leads to 3-6 percent more vehicle miles in the near term and 6-10 percent more over many years.
- Much of the traffic is brand new. Some of the cars on a new highway lane have simply relocated from a slower alternative route. But many are entirely new. They reflect leisure trips that often go unmade in bad traffic, or drivers who once used transit or carpooled, or shifting development patterns, and so on.
What’s significant about the Caltrans acknowledgement is that induced demand creates something of a mission crisis for transportation agencies that spend most of their money on building new roads. (The same can be said for peak driving.)
Conversely, reductions in roadway capacity tend to produce social and economic benefits without worsening traffic congestion. The removal of elevated freeway segments in San Francisco coupled with improvements to the at-grade Embarcadero and Octavia Boulevards has sparked an on-going revitalization of the surrounding areas while producing a significant drop in traffic.13 Many cities in Europe have adopted the strategy of closing streets in the central business district to vehicle traffic as an approach to economic revitalization,14 and this strategy is increasingly being adopted in cities the U.S., from New York City to San Francisco.
Good and short read, worth it for anyone who sits in traffic and wishes that there were five lanes of traffic instead of four.