To examine the effect of the ERP on different types of users, traffic demand elasticities were
calculated separately for different vehicle categories. The classification corresponds to the different
ERP charging classes, except that heavy goods vehicles, very heavy goods vehicles and buses were
combined. Table 7 shows the elasticity estimates for vehicles entering RZ in the morning peak hours
(7:30-9:30) while Table 8 presents similar data for two expressways (Pan-Island Expressway and Ayer
Rajah Expressway, 7:30-9:00) based on rate revision in October 1999. Figure 2 shows the comparison
of elasticities for different vehicle categories.
It seems that passenger car demand is the most elastic, with values of –0.106 and –0.195, for
Restricted Zone and expressways, respectively. Light Goods Vehicles show the lowest elasticity of
only –0.023 to –0.044. This illustrates the effectiveness of road pricing as an instrument to control
traffic congestion. The percentage of passenger cars is usually the highest among all vehicle
categories, always comprising over half of the total traffic volume. Its highest sensitivity to price
changes means that ERP can effectively control the total traffic volume on the road.