Study: Free parking benefits reduce public transit ridership

Wed, 2014-08-13 06:00 -- Doug Cooley

Coaxing downtown workers onto public transit and out of their cars is an aspiration of many city policymakers. Unfortunately, employers offering generous commuter perks may be thwarting their efforts.

That's the conclusion of Virginia Tech researchers who performed a study of commuter benefits. They found that when businesses offer their employees free office parking along with public transportation benefits such as free or subsidized bus passes, fewer workers use public transit. However, if employers eliminate the free car parking option but retain the public transit subsidy, the number of workers using commuter trains and buses goes up. 

“Benefits for public transportation … seem to work best when car parking is not free,” the authors state in their report. 

Unpacking the study

The commuter benefits study gathered transportation preferences of 4,360 regular commuters in the Washington, DC region. Researchers used the data to predict the probability of workers' commuting choices based on various benefit packages. Cycling and walking benefits -- such as employers providing lockers and shower facilities -- were also factored in as benefit variables, but proved statistically insignificant (below 2%) in all scenarios.

Here’s a summary of the predicted commuting probabilities based upon various benefit packages:

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No commuter benefits: When employers offer no perks, researchers predict that 76% of commuters will drive to work, and 22% climb aboard transit.

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Free car parking only benefit: In this scenario, the probability of commuters driving alone to work jumps, not surprisingly, to 96%. Transit ridership comes in at less than 3%.

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Public transportation only benefit: When employers provide only free or subsidized transit passes, the prediction is that only 23% of commuters drive and 76% opt for public transportation.

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Concurrent free car parking, public transportation and bike/walk benefits:  The prediction here is that 87% of commuters will chose to drive -- which is about 10 percentage points above the probability when no benefits are provided. It’s predicted that 12% will use transit.

A CityLab piece also digs into the data and builds graphs illustrating the findings. Its discussion concludes that the study is another example of how incentives to ride transit don’t really work. To change commuter habits, city officials have to provide disincentives to drive or park.

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