Analysis on Characteristic of 85th Percentile Speed and Suggestion on Speed Limit of Freeway

This paper analyzes on 85th percentile speed of different lane and vehicle type under different alignment condition and traffic condition.The multi-linear regression models are established between curve radius,angle,curve length and 85th percentile speed of different direction on freeway.Critical up-slope is given to need speed limit.The relationships are studied between traffic volume,traffic composition and 85th percentile speed of freeway.Speed distribution scope is presented under the condition of free flow.The relationship model is established between intermingling ratio of large vehicle and 85th percentile speed.Speed comparison is performed between rain and sunshine on freeway and the conclusion is presented that flurry has little influence on speed.