Delineator for Separated Bicycle Lanes at Sidewalk Level

The City and County of San Francisco sponsored research to identify a delineator for separated bicycle lanes at sidewalk level that is at least as detectable as truncated-dome detectable warning surface (DWS) by pedestrians with visual impairments, and that is not a barrier to pedestrians with mobility impairments. Tested as potential delineators were a 12-in. wide continuous raised trapezoid (0.75 in. high), and 12- and 24-in. wide installations of relatively wide flat-top bars (FTBs) and of a "corduroy" surface of narrower bars spaced more closely together (both 0.2 in. high). Thirty-one visually-impaired participants detected all five surfaces in addition to DWS, a total of six times each, from 90 degrees and 25 degrees approaches, with mean detection accuracies better than 90% for all surfaces (no significant differences). The long white cane intruded into the cycle track significantly less frequently with 24-in. wide surfaces. In a counterbalanced manner, participants also briefly stepped onto each surface eight times, each time identifying it as "domes,""bars," or "trapezoid." They identified the trapezoid significantly better (mean rate of correct identification = 98.8%) than all other surfaces. A majority of participants with vision disabilities preferred the trapezoid. Thirty participants with a variety of mobility impairments, using a variety of aids, crossed each surface four times with little significant difference from the DWS in effort, instability, and discomfort or pain. No surface was found to be a barrier to crossing. The trapezoidal surface was recommended as the delineator, although the 24-in. FTBs also performed very well.