The provision of park-and-ride (P&R) facilities helps make a transit system accessible to those that don’t live within walking distance of a stop. However, transit operators can’t afford to have parking at all stops because of the additional costs related to land acquisition, construction, and maintenance. Even if an operator had the resources to provide parking at every stop, this would not necessarily be an efficient use of resources. The benefits generated by a P&R lot will not always justify its costs, depending on the number and composition of the transit users it attracts.

One important factor that deserves greater consideration when assessing the benefits of a P&R facility is the marginal impact that P&R has on travel outcomes such as transit trips and vehicle miles traveled (VMT). In other words, consideration should be given to the net impacts relative to a scenario in which a P&R facility does not exist. This accounts for the possibility that some portion of those using a given P&R facility might otherwise continue to use transit. Further, some P&R users might otherwise choose an alternative travel option that requires more or less driving than the current distance they travel getting to the P&R facility.

If the marginal increase in transit usage and/or the marginal decrease in VMT associated with P&R facilities are small, it becomes difficult to justify resources being dedicated these facilities when they might generate more benefits when invested in other aspects of the transit system. Unfortunately, the marginal impacts of P&R facilities are not well established, particularly in a US context. The data needed to calculate such impacts is rarely collected. Traditional travel surveys don’t ask the right types of questions. In a recently published study that I co-authored with Jason Cao (a colleague at the University of Minnesota), we attempted to fill this gap in knowledge using a survey of P&R users from the Twin Cities region in which the questions were specifically designed to determine how respondents would react to the removal of a P&R facility. The key survey question for this study reads as follows: 

If a park-and-ride facility did not exist at the stop/station where you went on the train/bus, how would you have made this trip?

Respondents then picked their preferred response from a detailed, cascading menu of possibilities. One of the possibilities was to choose a different P&R facility. However, those that initially chose this option were then asked how they would make the trip assuming there was no feasible P&R option.

A key finding from the survey responses is that, when treated as whole, the system of P&R in the Twin Cities generates significant marginal benefits, both in terms of increasing ridership and reducing VMT. Over 80% of the surveyed P&R users said they would only use transit if they had access to a P&R facility. Assuming the survey responses accurately reflect the preferences of the regional population of P&R users, the P&R system creates a net increase of nearly 15,000 daily riders. If the survey respondents no longer had any P&R option, they would generate an average of 19 additional VMT per round trip. Based on this survey average, the entire P&R system generates a net reduction of over 350,000 VMT per day. 

The next key finding is that, while the transit use of most survey respondents depends on the availability of P&R, it does not depend on the presence of any particular facility. When no longer able to use their current P&R facility, most would choose an alternate P&R location rather than quitting transit. As such, a judicious reduction in the size and/or quantity of P&R facilities may result in cost savings to the transit operator without much loss in ridership or increase in VMT. 

The facilities with the weakest marginal impacts (daily riders as low as 0.09 per parking space and daily VMT reduction as low as 3.9 per parking space) may provide the best targets for system contraction. These underperforming facilities tend to be of two types: 1) those with low utilization rates (i.e., the ones with the emptiest parking lots) and 2) those in closest proximity downtown Minneapolis, which is the final destination for over 90% of the survey respondents. The latter is explained by the fact that many P&R users choose the facility that allows them to remain in their own vehicle for as much of the trip as possible, while passing up other facilities that are closer to home. Thus, removing downtown-proximate facilities encourages P&R patrons to choose a closer facility that requires less driving.

A major caveat to any recommendations about P&R contraction is the feasibility of such actions. The current users would likely resist, even those that have a good alternative. Those that planned and approved the placement of a given facility may have a natural bias towards it preservation. In some cases, these facilities are multi-story structures that were costly to build and would be costly to remove, making it easier to justify their continued presence even when underperforming. Further research is needed to better understand the political and institutional barriers that may prevent closing and/or resizing of inefficient P&R facilities. Alternatively, since new P&R facilities wouldn’t have the same level of political protection, the lessons of this research might be more readily applied to decisions about if and when to build them to begin with. 

Broadly speaking, our study demonstrates that building an efficient P&R system first requires an understanding of the demand for P&R facilities within neighborhoods, and then careful planning in terms of the size of these facilities and how far apart they are from each other so that resources are not wasted on unused parking spaces. Further, to maximize VMT reduction, P&R facilities work best in outlying areas where the distance between the users’ homes and their transit stops is minimized and the transit portion of the trip substitutes for longer driving trips.

The feature image is from Pexels.