Exploration of 85th Percentile Operating Speed Model on Horizontal Curve: A Case Study for Two-Lane Rural Highways

The purpose on this paper is to develop the 85th percentile operating speed models at mid-curve that can be integrated based on speed at the approach tangent line and radius of simple horizontal curves. This research paper presents an empirical research and presents the empirical model to predict the 85th percentile operating speed models for the horizontal curve on Malaysian two-lane rural highways conditions. The speed data measurement is based on Spot Speed Data at specified points and location using instrumentation called Laser Gun Meter Detector. Multiple linear regression equations were developed to predict the V85 of vehicles on horizontal curves in two-lane rural highways. The geometric parameters such as radius of curve and speed at the approach tangent line are used to recognize the effect of V85 operating speed models at the mid-curve. If this 85th percentile operating speed prediction model using multiple linear regression analysis is implemented and enhanced into current guideline and standard in Malaysia, it could play an important role in designing or redesigning of the horizontal alignment for two-lane rural highway in Malaysia.