Parking offset, i.e., distance between the curb and a parked car, was measured along two multilane urban arterials in Brookline, MA with parking lanes ranging from 6 to 9 ft wide. There were 469 observations, with more than 100 observations each for 6, 7, 8, and 9 foot parking lanes. As parkinglane width grew in progression 6-7-8-9 ft, the fraction of cars parked more than 12 inches from the curb, the legal limit, increased in a corresponding progression 1%-13%-44%-60%. Mean parking offset increased by 3.7 inches with each additional foot of parking lane width (0.3 ft/ft or m/m). Weargue that 95-percentile parking offset is a better measure of impact on bicyclist operating space, because when riding next to a parking lane, cyclists tend to choose a path that envelopes most parked cars, requiring oneto deliberately maneuver around only about one parked car out of twenty. 95-percentile offset increased by about 5 inches with each additional footof parking lane width (0.44 ft/ft or m/m). Multivariate regression indicates that wide vehicles (e.g., vans, large SUV’s) tend to compensate by parking a little closer to the curb; meanwhile, effects of adjacent lane width, whether there is an adjacent bike lane, and parking regulation type (meter or not) were not found to have a significant impact on parking offset.These results imply that additional operating space for bicycling can be provided by marking narrower parking lanes. American guidelines, with “desirable minimum” recommended widths of 8 ft (7 ft on local streets), and maximum widths of 10 or 12 ft, do not recognize this possibility of driver response, and are contrasted with Dutch guidelines, which recommend parkinglanes widths between 6 to 6.5 ft (1.8 to 2 m), plus a marked buffer when there is an adjacent bike lane.
Samenvatting