Your Mother-in-Law Should Take the “El” and Other Insights Into the Value of Public Transportation

Have you ever wondered what rush hour would look like if public transportation was not an option? Empirical evidence has finally validated the conventional wisdom: the more people who take public transportation, the less time is wasted in traffic. Economist Michael L. Anderson demonstrates, in his article “Subways, Strikes and Slowdowns: The Impacts of Public Transportation on Traffic Congestion,” that a halt in mass transit operation, due to a 2003 strike, caused a 47 percent increase in traffic delays in Los Angeles.  Further, he found that the total economic benefit of congestion relief in the LA metropolitan area, “is between $1.2 billion to $4.1 billion per year”. The public benefit of congestion relief alone, according to the author, is enough to “justify [mass] transit infrastructure investments”.

This is welcome information in a country where “public transportation received 23 percent of federal highway and transit outlays but accounted for 1 percent of passenger miles traveled”. The prevailing majority of academic literature in the field suggests that this type of mass transit spending may be imprudent based on estimates which indicate that public transportation offers very little for automobile commuters in terms of congestion relief. However, according to the author, these models fail to accurately represent intra-city congestion heterogeneity. By accounting for variable levels of traffic on different roadways throughout the city, Dr. Anderson’s model predicts an effect around six times larger than previous studies.

The simple logic behind this model is that public transportation is more appealing to those commuters who face longer traffic delays. Each additional automobile on a roadway with greater congestion has a “higher marginal impact on congestion” relative to an additional automobile on an average road. Therefore, by removing drivers from the most highly congested roads, mass transit provides a greater benefit than if one assumes that all roads are equally congested.

The author validates this logic using highway speed data from the time period around and during a 2003 strike by the Los Angeles County Metropolitan Transportation Authority (MTA). Using a regression discontinuity design to compare average traffic delays directly before and after the start of the strike, Dr. Anderson estimates that while mass transportation systems were shut down during the strike there was an increase in average delays by 0.19 minutes per mile (47 percent) during peak hours. He goes on to estimate that the “congestion relief benefit per peak-hour transit passenger mile” is between $1.20 and $4.10 in the short-term.

The author cautions that the long-term benefits mass transit provides in terms of congestion relief are likely to be less than the previously cited amount, as individuals adapt to increases in congestion (mainly by reducing total travel).  However, even the diminished long-term benefits are four times larger than previous estimates. Dr. Anderson also warns that these conclusions only apply to the Los Angeles metropolitan area. Studies like this help to validate public expenditure on mass transit infrastructure and add credence to the argument that more investment is needed.

Feature Photo: cc/(David Ohmer)