A Warranty Analysis of Grade Separated Pedestrian Crossings of Urban Roadways

In order to set grade separated pedestrian crossing facilities reasonably on urban road sections and ensure the safety of crossing pedestrians,the video observation method was used to obtain the waiting time of crossing pedestri-ans,traffic conflicting times and driving speeds at an un-signalized crosswalk on an arterial road with two-way six lanes. Calculation formula of vehicle dispersing time was proposed,and the warrant of traffic volumes was defined for grade sep-arated pedestrian crossing facilities according to investigated threshold value of crossing pedestrians′ tolerable waiting time.Based on observed data,regression method was applied to establish relationship model between pedestrian-vehicle traffic conflicting times and vehicle driving speeds.The warrant of driving speed for grade separated pedestrian facilities was determined based on the relationship between stopping sight distances and the width of conflict zones.The warrant of pedestrian volumes was defined by calculated design capacity of signalized crosswalks.The results show that grade separa-ted pedestrian crossing facilities are warranted when vehicles’dispersing time of any direction is more than 60 s during one cycle in peak hour,or driving speed is more than 50 km/h,or crossing pedestrian volume is more than 2 200 person/(hg·m).