Parking Lane Width and Bicycle Operating Space

This study tests the hypothesis that marking narrower parking lanes can create additional operating space for bicyclists by inducing motorists to park closer to the curb. Parking offset (i.e., distance between the curb and a parallel parked car) was measured along two multilane urban arterials just outside Boston, Massachusetts, with parking lanes ranging from 6 to 9 ft wide. As parking lane width grew in progression from 6 to 7 to 8 to 9 ft, the fraction of cars parked more than 12 in. from the curb, the legal limit, increased in a corresponding progression from 1% to 13% to 44% to 60%. The authors argue that 95 percentile parking offset is a better measure of impact on bicyclist operating space than is mean parking offset, because when riding next to a parking lane, cyclists tend to choose a path that envelopes most parked cars, such that they need to deliberately maneuver around only about one parked car out of 20. With each additional foot of parking lane width, 95 percentile offset increased by about 5 in., for a response of 0.44 ft/ft or m/m. Multivariate regression indicates that wide vehicles (e.g., vans, large sport–utility vehicles) partially compensate by parking about 1 in. closer to the curb. Effects of adjacent lane width, whether there is an adjacent bike lane, and parking regulation type (meter or not) were found to have no significant impact on parking offset. These results imply that in cities that display this level of response to parking lane width, additional operating space for bicycling can be gained by marking narrower parking lanes.