Researchers Study Impact of Transitways on Nearby Roads, Park-And-Ride Choices

November 18, 2021
Light rail station in Minneapolis
New Humphrey School research shows a significant decline in nearby vehicle traffic once the Green Line light rail service began carrying commuters between Minneapolis and St. Paul. Photo: iStock

How does a transitway affect automobile traffic on nearby roadways? What factors influence which park-and-ride facilities people choose? These two questions were the focus of a recent two-part project by researchers at the University of Minnesota.

Transitways—such as dedicated light-rail transit (LRT) and bus rapid transit corridors—have the potential to mitigate growing traffic volumes and relieve congestion on nearby roads by prompting some drivers to make the switch to transit. There was little research of this effect, however, for the Green Line LRT between Minneapolis and St. Paul.

Green Line leads to decline in nearby traffic

Using extensive traffic data before and after the opening of the Green Line, researchers led by Humphrey School Professor Jason Cao exam­ined the impact of the line on road traffic within and outside of LRT influence areas. They con­trolled for a wide range of variables such as transit service, land use, and road classes.

The team found that in its first two years of operation, the Green Line reduced traffic on nearby roads by 22 percent compared with roads outside its influence area (defined as within a mile from the line). In the next two years, vehicle traffic on nearby roads bounced back by about 6 percentage points.

“This rebound was likely due to land-use development spurred by the Green Line, and by travelers who switched from other routes and modes,” says Cao. “Overall, the Green Line had a significant influence on nearby road traffic, and this influence keeps evolving over time.”

The Minnesota Department of Transportation (MnDOT), a project sponsor, will use the data and findings in its transit evaluations and planning.

“This project highlights how a transit investment may benefit not only transit, but also other transportation modes,” says Jim Henricksen, director of travel behavior analysis with MnDOT’s Metro District.

Park and ride users prefer less driving, fewer transfers

For the park-and-ride (PNR) portion of the project, researchers led by Alireza Khani in the Department of Civil, Environmental, and Geo- Engineer­ing examined responses to Metro Transit’s 2016 on-board sur­veys, which provided trip attributes and demographic information about riders. Findings from the PNR trips in the survey include:

  • PNR users chose a route with a high proportion of time on transit—not necessarily the fastest overall travel time. On average, they chose a route that took 17 percent longer than the shortest route available to them.
  • Users preferred to minimize driving time and transfers. They viewed travel time in a car as four times more burdensome than the same amount of time traveled by transit. Adding a transfer was seen as equivalent to an additional 17.5 minutes of transit time.
  • Users’ behavior indicated that transitway routes had higher utility than comparable express bus routes. A transitway route was viewed as favorably as an express bus route that was 16.6 minutes faster.
  • Users favored PNR facilities that were served by transitways and that had more amenities.

The PNR model will help planners design, size, and locate facilities that are both appealing and convenient for transit users and determine which facilities to prioritize for major maintenance and renovations.

The model “provides insight into what is important to park-and-ride users and enhances our ability to forecast future demand,” Henricksen says.

The project was part of the Transitway Impacts Research Program. More Information: 

This story was originally published by the Center for Transportation Studies  

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