Off-street parking access linked to higher VMT

When it comes to parking in new residential developments, planners often face stakeholders with two opposing viewpoints. Some want land-use authorities to require lots of off-street parking in order to avoid over-demand for street spots. Others complain that providing copious off-street parking will induce more traffic; if authorities require anything, they should set parking maximums, not minimums.

A new study by Rachel Weinberger of the University of Pennsylvania provides evidence for the latter view.

She looked at commuting travel behavior for residents of three New York boroughs – the Bronx, Brooklyn and Queens – who worked in Manhattan.Her focus on residential areas contrasts with what is more commonly studied, the effect of parking supply on behavior in central business districts.

Controlling for median tract income, age of housing stock, vehicle availability, tract level transit accessibility, transit served destination and other variables, we find that tracts with higher levels of on-site parking have higher levels of drive mode share to the transit rich Manhattan core. Thus we conclude that guaranteed parking at home is a contributing factor to a worker’s decision to drive to work. From this we infer that driving to other activities is also likely to be higher.

What about neighbors’ concerns that limited off-street parking will cause street parking to fill up?

To the extent that additional driving is the product of increased parking supply these residents may be trading parking ease for traffic congestion and additional energy consumption. Furthermore, on-site parking requires curb access, which reduces existing parking supply (Weinberger et al., 2008b). Thus on-site parking requirements, which require thousands of curb-cuts, far from protecting existing residents’ enjoyment of the street system, compromise that enjoyment on two counts.