Passenger Car Equivalents for vehicles on Singapore expressways

It is a common practice to use Passenger Car Equivalent (PCE) as a standard measure in highway design and analysis. PCE values recommended in the U.S. Highway Capacity Manual and those used in the U.K. have been adopted by many Asian countries. However, this adoption may not be appropriate since traffic conditions and driver behavior can be quite different. Results from this study, conducted on the rather flat terrain prevalent in Singapore, indicate that a different set of values should be used for the analysis of traffic on Singapore expressways. For motorcycles, a PCE of 0.4 is more appropriate than the value of 0.75 formerly used in the U.K., indicating a much smaller effect on traffic. For light trucks, heavy trucks, and buses, their PCE values are estimated to be 1.3, 2.6, and 2.7, respectively. These are higher than those recommended for use in the U.S. and U.K. implying a more severe individual impact on traffic in Singapore. The higher values are believed to be due to the lower legal speed limit of 50km/h for these vehicles. In addition, expressway capacity in Singapore appears to be around 2400 passenger cars per hour per lane, considerably higher than standards used in both U.K. and U.S. practices.