Electronic Road Pricing system known as ERP was introduced in Singapore in September 1998 in order to tackle problems of over-congested roads. The scheme consists of ERP gantries located at all roads linking into Singapore's central business district. They are also located along the expressways and arterial roads with heavy traffic to discourage usage during peak hours. The gantry system is actually a system of sensors on 2 gantries, one in front of the other. Cameras are also attached to the gantries to capture the rear license plate numbers of vehicles. Currently, there are 80 ERP gantries in Singapore. A device known as an In-vehicle Unit (IU) is affixed on the lower right corner of the front windscreen within sight of the driver, in which a stored-value card, the CashCard, is inserted for payment of the road usage charges. The second generation IU accepts Contactless NETS CashCard and EZ-Link. The cost of an IU is S$150. It is mandatory for all Singapore-registered vehicles to be fitted with an IU if they wish to use the priced roads. When a vehicle equipped with an IU passes under an ERP gantry, a road usage charge is deducted from the CashCard in the IU. Sensors installed on the gantries communicate with the IU via a dedicated short-range communication system, and the deducted amount is displayed to the driver on an LCD screen of the IU. The charge for passing through a gantry depends on the location and time, the peak hour being the most expensive. If a vehicle owner does not have sufficient value in their CashCard (or EZ-Link) when passing through an ERP, the owner receives a fine by post within two weeks.
Since the introduction of a new scheme took place the system has shown some reasonable impact upon the overall level of congestion. The LTA(Land Transport Authority) reported that road traffic decreased by nearly 25,000 vehicles during peak hours, with average road speeds increasing by about 20%. Within the restricted zone itself, traffic has gone down by about 13% during ERP operational hours, with vehicle numbers dropping from 270,000 to 235,000. It has been observed that car-pooling has increased, while the hours of peak vehicular traffic has also gradually eased and spread into off-peak hours, suggesting a more productive use of road space.