Marlon G. Boarnet
Doug Houston (UC Irvine)
Andy Hong, Jeongwoo Lee, Xize Wang, Weijie Wang, and Steven Spears (UC Irvine)
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Los Angeles, the world’s prototypical automobile city, is transforming into a multi-modal metropolis. The six rail transit lines projected to open between 2012 and 2020 will make the Los Angeles Metro Rail system longer than the present day Metro in Washington D.C. At the same time, ambitious state regulations require that metropolitan planning organizations demonstrate how their transportation plans meet greenhouse gas emission (GHG) reduction targets. There is a pressing need to evaluate the impact of new transportation investments comprehensively. Yet, transportation, as a field, has rarely systematically evaluated the impact of major projects using an experimental – control group design. To help close that gap, we conducted the first-ever experimental – control group, before – after study of the impact of a major transportation investment in California.
As transportation becomes more varied – with localities experimenting with programs that include real-time parking pricing, toll lanes, neighborhood vehicles, and bicycle plans – it will be increasingly important to evaluate the impact of these projects in a consistent and credible way. Social scientists have applied the methods of experimental research designs for decades, but such techniques have only recently made inroads in transportation.
We conducted a detailed study of travel behavior changes around new Expo Line light rail stations, using experimental methods. The Exposition (Expo) Line is a light rail line in the Los Angeles metropolitan area that extends south and west from downtown Los Angeles. Phase I of the line, which opened in two stages in April and June 2012, runs 8.7 miles from downtown Los Angeles westward to Culver City, near the junction of the 405 and 10 Freeways. The six western-most stations along the Expo Line (Phase I) comprise the experimental neighborhoods, and similar control group neighborhoods were chosen nearby. This research project enrolled experimental households, within ½ mile of a new Expo Line station, and control households, living beyond ½ mile from the station. In fall of 2011, those households were asked to track their travel for seven days, recording daily odometer readings for all household vehicles and logging trips by travel mode and day for each household member 12 years or older. In approximately half of the households, an adult also carried a geographic positioning device (GPS) and an accelerometer, to measure travel (via the GPS device’s location tracking function) and physical activity. The same households were invited to complete the seven day travel study again in fall, 2012, after the Expo Line opened. In total, 204 households (103 in the experimental neighborhoods, 101 in control neighborhoods) completed the travel tracking before and after the Expo Line opened.
We used those data to conduct before-after evaluations of the impact of the Expo Line on travel behavior. The research design is a classic “differences-in-differences” approach. The impact of the Expo Line can be inferred by examining experimental minus control group differences and how those differences change after the Expo Line opens relative to baseline, “before opening” experimental minus control group differences. The travel behavior variables studied are household daily averages for: vehicle miles traveled (VMT), car driver trips, train transit trips, bus transit trips, walking trips, bicycle trips, walking minutes, and bicycling minutes. Additionally, we studied changes in physical activity for the adults who carried an accelerometer, and CO2 emissions for household vehicles.
The analysis gives the following results.
Summary and Policy Implications
Los Angeles has made a substantial commitment to rail transit, but several policy questions continue to be debated. Among those questions, possibly the most basic is whether new transportation options will change travel modes, and whether Angelenos will modify their travel as new options become available. Against that backdrop, the results from this research are in some ways striking. We find evidence that the Expo Line is associated with large reductions in VMT, some increase in rail transit ridership, changes in physical activity, and large reductions in GHG emissions among households living within ½ mile of a station. The research design, using a control group to account for factors other than the rail investment, allows us to make causal inferences more strongly than is often the case in social scientific research. In short, the Expo Line is associated with travel behavior change, and we can infer that the association reflects a causal effect of the Expo Line on household travel. The large impacts for VMT and GHG reduction occur within a small area – ½ mile around six new stations. Viewed from the perspective of the greater Los Angeles region, these impacts will be small, but they are large in the neighborhoods surrounding the Expo Line.
Several policy implications follow. First, this is some optimistic evidence for the rail transit investment program in Los Angeles. We did not conduct a formal benefit-cost assessment, but clearly the rail line is associated with changes in travel behavior that are consistent with the anticipated effects. Second, the evidence indicates that the travel impacts of light rail are enhanced by local land use characteristics. Bus lines and streets with narrower width are likely to be more conducive to increasing the effects of rail transit, at least based on the results from this study. Third, economic theory predicts that the travel impacts documented here will likely lead to downstream effects including changes in the resident population near Expo Line stations, changes in land prices (and hence rents and house prices), and changes in land uses. It is too early to draw conclusions about those downstream effects, and whether they will advantage existing residents or new residents or a combination of both. Yet, the fact that the Expo Line has changed travel behavior suggests that the rail service is valued by nearby residents. That value will likely be reflected in land prices and land uses in later years, which will lead to broader social and economic impact around the rail transit lines.
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Funding for the study was provided by the Haynes Foundation, the Lincoln Institute of Land Policy, the Southern California Association of Governments, the University of California¹s Transportation Center and Multi-Campus Research Program on Sustainable Transportation, and the USC Lusk Center for Real Estate.