Exploring the extent of critical gap acceptance caused by rainfall in Malaysia

Abstract

At a priority intersection, critical gap is the threshold by which drivers judge whether to accept a gap or retain holding position. It is usually taken as a fixed value or considered to follow a certain distribution. Critical gap is needed at roadway segment to allow road user to make decisions relative to the lead vehicle. If the critical gap is larger than reaction time, drivers maintain safe following distance from the vehicle in front; otherwise the probability of vehicle collusion is heightened. The paper is aimed at determining critical gap acceptance at roadway segment under rainfall condition. Differential gap is expected under dry and rainfall conditions irrespective of rainfall intensity due to reduced visibility. Based on the hypothesis that rainy conditions have effect on critical gap acceptance, impact studies were carried out at Pontian-Skudai Route 5, Malaysia. The objectives are to estimate average gap and determine critical gap acceptance under prevailing conditions. In a 'dry and rainfall impact study', traffic stream gap was calculated from the headway, flow, length of vehicle and speed relationship. Headway was mainly derived from maximum flow rate. Results show that average traffic stream gap for dry weather is higher than that of rainfall conditions. However, motorists maintain a safe following distance under both circumstances. The paper concluded that rainfalls irrespective of their intensities have no significant impact on critical gap acceptance. These so because all observed vehicles on the roadway under rainy conditions are affected and there is no undue advantage enjoyed by any particular type of vehicle. Exploring the extent of critical gap acceptance caused by rainfall in Malaysia. Available from: https://www.researchgate.net/publication/289618994_Exploring_the_extent_of_critical_gap_acceptance_caused_by_rainfall_in_Malaysia [accessed Sep 27, 2017].