Contrarian research: Transit relieves congestion, but park-and-rides do not

By Robbie Webber

Research using the results of a 2003 Los Angeles County Metropolitan Transportation Authority strike shows that transit does indeed relieve congestion, but only along corridors that parallel heavily used lines. At the same time, research in the Netherlands indicates that park-and-ride lots in cities may actually increase vehicle miles traveled in a metro area.

Both those arguing in favor of and against increasing transit operations and subsidies have long accepted Down’s Law of Peak Hour Expressway Congestion, which states that on urban commuter expressways, peak-hour traffic congestion rises to meet maximum capacity. If transit doesn’t relieve congestion, is there an economic argument to justify subsidies?

Michael Anderson, an economist at University of California-Berkeley, showed that there is congestion relief and an economic justification for transit as well. He posited that commuters facing the worst congestion would choose transit more readily. Those that faced less congestion would continue to drive. This theory was tested when a transit strike shut down bus lines and subways in Los Angeles County. Indeed, the corridors that paralleled heavily used transit lines experienced an average 47 percent increase in delay, and one corridor experienced a 90 percent increase in delay, while corridors in neighboring counties unaffected by the strike showed a statistically insignificant change in delay. Without transit, congestion increased significantly.

Obviously, there are other benefits to transit ranging from reduced tailpipe emissions to social justice. But Anderson’s research also shows that the economic benefits may have been underestimated.

Our estimates imply that the total congestion relief benefit of operating the Los Angeles transit system is between $1.2 billion to $4.1 billion per year, or $1.20 to $4.10 per peak-hour transit passenger mile.

Another study found that park-and-rides may actually increase vehicle miles traveled in metro areas. Giuliano Mingardo’s research in The Hague and Rotterdam in the Netherlands questioned conventional wisdom regarding park-and-ride lots. Instead of taking cars off the road, park-and-ride lots may encourage driving.

Travelers at the lots were surveyed about what they would have done if the parking was not available. Many would have accessed transit by bicycle or would have transferred from another transit line. Others were not using transit at all, but parking in the lot and walking to nearby destinations. Finally, the survey found that some respondents were actually visiting the city more often – via the park-and-ride – and therefore making driving trips they would not have made previously.

Mingardo suggested that park-and-ride lots far out in the suburbs functioned better at decreasing driving. Those that facilitated driving were located in areas with other means of transit access. Those using the lots were also willing to pay higher parking prices, and he suggested that proper pricing and monitoring by the city could counteract the effect of abundant, free, or cheap parking.

Robbie Webber is a Senior Associate at SSTI.