Safe braking distance at signalized intersection

Abstract

Signalised intersection is an area where most of the drivers having dilemma in making decision to either pass through the intersection or stop when the light turns to yellow. During this phase, a sudden deceleration and incorrect estimate of intersection clearance time cause rear-end collision, severe right-angle crash and left-turn head-on collision. Therefore, the aim of this study was to determine the safe braking distance at signalised intersection by using the concept of stopping sight distance, so that a set of road marking and road sign can be proposed to help the driver in making decision within the dilemma zone. Samples of vehicle’s approaching speed were collected at a signalised intersection within the Ipoh-Lumut Highway in Perak Tengah. Statistical analysis showed that the observed 15th and 85th percentile speed at the intersection were 66.2km/h and 88.5km/h, with a mean and standard deviation of 77.5km/h and 9.99km/h. Goodness-of-fit tests showed that the distribution of the approaching speed at the intersection was normally distributed with a probability of 14.4%. It was concluded that safe braking distance from the stopping line of the signalised intersection is between 97m for lower speed limit to 152m for the upper speed limit.