Green Shared Lane Markings on Urban Arterial in Oakland, Caliornia

In 2013, the City of Oakland, California, implemented a green shared lane (i.e., super sharrow) treatment, which consisted of a continuous band of green color on the pavement in conjunction with shared lane markings (i.e., sharrows) as an experimental traffic control device. The implementation was an attempt to improve traffic operations on a multilane urban roadway frequented by cyclists but for which geometric constraints prevented installation of dedicated bicycle lanes. The purpose of the experiment was to promote (a) safe and legal lane positioning by cyclists and (b) safe and legal passing by motorists. Through statistical analysis, the effects of the green band (i.e., green shared lane) on user behavior were isolated for comparison with the effects of no bikeway striping and standard sharrows. The key findings were (a) the green shared lane led cyclists to ride farther from parked cars (i.e., outside of the door zone) than they did with standard sharrows; (b) standard sharrows and the green sharrow lane led motorists to shift more often from the right to the left travel lane than they did with no bikeway striping; (c) the average passing distance for motorists who overtook cyclists did not change significantly; (d) the percentage of motorists who left 3 ft or more when they passed decreased with the presence of the green sharrow lane; and (e) the green shared lane had no negative operational effect on auto operations, auto speed, or transit speed.