By Michael Brenneis
Conventional thinking holds that congestion stifles the economy. Sitting in traffic or having it take longer to get someplace important would seem to be a drain on productivity. On the contrary, a group of Texas researchers looking at travel survey data from the Puget Sound area of Washington State found that travelers exposed to traffic congestion and travel delay will simply find a means of getting from point A to point B that doesn’t rely on driving. Their novel approach incorporates data on whether people choose to live in places that support their preferred travel options or way of life, addressing the question of residential self-selection.
The authors compared free-flow and peak-period travel times for each household in the survey and calculated a corresponding delay score. They found that as roads get more congested and for each point that the delay score increases, the number of trips taken by a household falls by 16% and its vehicle miles traveled (VMT) drops by about 12%.
Other interesting model results include that households with good transit access have somewhat lower VMT—a drop of about 6%—and that access to free parking tends to increase daily VMT by about 31%. Also, households in congested areas tend to own fewer cars.
As the costs of driving—say the price of gas, tolls, or delay due to congestion—go up, people modify their travel behavior to accomplish their daily travel needs with other modes, often at a lower cost. Traffic congestion can be reduced as people begin to use other means to get around. For those populations that are more mobile, and can afford higher housing costs, moving closer to essential destinations and to places with good walkability can further reduce the need to drive, and the associated traffic.
Additional lanes are often considered the traditional cure for congestion and delay. One problem with this strategy is that it tends to induce more car travel and encourage development on the periphery, which increases the travel distance between destinations, increases maintenance costs, makes transit less sustainable, and further lengthens travel times. This new study shows that congestion may be a positive force in encouraging people to find more sustainable ways to get around, and validates the idea of induced demand.
If people who are exposed to congestion and delay are naturally finding other, more sustainable means of getting around, that undercuts the need to invest in more road capacity. In fact, some agencies are leading the way in shifting priorities to make walking and bicycling more attractive for shorter trips, make transit more attractive for longer trips, and design cities so that reaching essential destinations can routinely be accomplished by means other than driving a car.
Giving people the choice to not travel by car can help address the paradox of congestion being more likely in denser areas, mentioned in this paper. The authors list some potential strategies like increasing density near transit corridors, demand management practices such as pricing and parking reform, and transit investments. Other options include improving walking and bicycling facilities, and zoning reform that encourages clustering housing, jobs, and essential destinations.