It's Amazing How Many More Commuters Would Drive Less if They Didn't Get Free Parking

The lure of the space overwhelms almost all other commuter benefits.

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Victoria Pickering/Flickr

If you're an employer in a major metro area, it's in your best interest to offer a commuter benefits plan for every worker, regardless of their preferred travel mode. That typically means free parking for drivers, subway or bus pass programs for transit riders, and secure bike storage as well as maybe showers for cyclists. This seems only fair, like a bit of a win for everyone involved.

Thing is, commuter benefits for everyone can end up being a loss for the city itself. That's because the lure of free office parking is so great that it not only neutralizes the other benefits, it actually entices some commuters into their cars and out of the alternative mode they might otherwise prefer. So what looks at first like a balanced policy in fact ends up favoring drivers—and that means more traffic for the whole city.

To illustrate the problem, let's consider a new analysis of commuter benefits from Virginia Tech transport scholars Andrea Hamre and Ralph Buehler. Hamre and Buehler analyzed a household travel survey of 4,630 people with full-time jobs in the metro Washington, D.C., area (both in the city core and the inner suburbs). The survey noted each person's commute mode as well as any commuter benefits received at work.

Using the data, Hamre and Buehler predicted the probability of commuters driving alone or taking transit to work, based on the benefits package their employer offers. We converted that data into the charts below.

At baseline, when employers offer no commuter benefits at all, the probability of driving alone to work is nearly 76 percent, with taking transit at 22 percent (below, orange dots). As expected, when a company offers only free parking and no other benefit, the probability of solo-driving nearly hits the roof, reaching 97 percent (blue). Similarly, when a company offers only transit benefits and nothing else, probability of taking the bus or train breaks 76 percent, and driving becomes less appealing (light blue).

So far, no surprises. But take a look what happens when a company gives employees both free parking and transit perks. These commuter benefits don't cancel each other out. If they did, we'd expect to see probabilities similar to the scenario when there were no benefits at all. Instead, we find the probability of driving alone to work in this scenario increased relative to nothing—reaching roughly 83 percent, compared to 16 percent for transit (below, dark blue).

When we pull in data on cycling and walking, little changes. These two modes were both at or below 1 percent probability for most benefit scenarios (they peaked at 2 percent walking and 1 percent cycling when only bike-ped benefits were offered, with no other commuter perks). Even when we add these tiny probabilities to transit for the previous benefit scenarios and create one lump alternative mode, driving alone still dominates. And when we add bike-ped benefits to the mix with free parking and transit perks, the probability of driving actually rises toward 87 percent (below, purple).

So here's the trouble: As far as a city is concerned, its transportation system may actually function better when employers offer no commuter benefits than when all workers are covered regardless of mode. Benefit scenarios that include free parking "overwhelm or render insignificant" any perks related to public transportation or other alternative modes, in the words of the researchers. Hamre and Buehler conclude:

While benefits for alternatives to driving are associated with individuals choosing to walk, cycle, and ride public transportation, free car parking is associated with driving, and the joint provision of free car parking along with these other benefits may blunt the efficacy of efforts to get commuters to walk, cycle, and ride public transportation to work.

Again, it's hard to blame a company for offering free parking, especially if it draws talented workers from parts of the suburbs with poor transit. There are plenty of ways to emphasize alternative commutes, of course, but few employers do so to the exclusion of other modes; just 7 percent of people in the D.C. survey worked at places with transit-only commuter benefits. And in cities with transit systems less robust than the D.C. Metro, that approach is no doubt tougher.

In the end, what the data give us is yet another example of how incentives to ride transit aren't enough to shift commuter preferences on their own. If cities want real change, they need to create disincentives to drive or park, too.

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