It is generally accepted that a fully Vehicle Actuated control (VA) is almost always the most efficient form of traffic signal contr l for an isolated intersection. The successful design of VA control requires the specification of several critical parameters, including detector position and the settings for the timing variables. The major timing variable related to vehicle delay is vehicle extension (Bullen, 1989). This paper describes the examination and evaluation of the erformance of VA control under mixed traffic conditions with particularly high roportion of motorcycles. This includes an investigation of the most appropriate extension time for the VA control that was suitable for mixed traffic. As the proportion of motorcycle in traffic is high, the effect of motorcycles to the performance of the VA control was also investigated. Two schemes were carried out to observe it, namely: sc eme 1 where detector detects all vehicle types (DfT, 2006) and scheme 2 where detec or detects all vehicles types, apart from motorcycles. The simulation program VISSIM was used to examine and analyse the performance of the VA control in term of a rage delay of vehicles at an intersection. The simulation results show that the Vehicle Actuated Controller (VAC) System D using extension time of 1.2 seconds and VAC Extension Principle with detector position of 30 m and extension time of 3.0 se nds produced better performance than the other extension times tested for both schemes. The simulation results indicate that the performance of the VACs with scheme 1 is generally worse than with scheme 2. The performance of the VACs with scheme 1 against 2 tended to reduce significantly as the percentage of motorcycles in traffic increased
