Sir

Recognizing the high economic and environmental costs of traffic gridlocks, Singapore recently implemented an electronic road pricing (ERP) system, the first of its kind in the world. Using a network of overhead gantries straddling the central business district and the approach routes and expressways leading there, the system works by remotely debiting tariffs from a smart card installed in a slot near the vehicle's windscreen. Infringement is registered by capturing the image of the vehicle's number plate. Our experience of this system, phased in during 1998 and 1999, offers some perspectives to other regions contemplating the use of this technology to manage congestion.

A major barrier to the implementation of electronic tolling is public aversion to infringement of privacy. In the passive electronic toll systems used in some parts of Australia, Canada, Europe and the United States, vehicles need to be tagged and their movements monitored for monthly billing. Singapore instead chose the cash-card system, in which direct debiting removes the need for billing and debt collection.

There needs to be political courage in implementing congestion tolls. Singapore ran a public education campaign to show that ERP is about reducing vehicle usage, not making money. Indeed, revenue has plunged by about 40% compared with the previous, manual tolling system, since fewer drivers use the tolled roads. The government absorbed the cost of fitting every vehicle in Singapore with a unit for cash cards, gave road-tax rebates and reduced customs and registration costs for new cars, so motorists saved money. This has helped public acceptance of ERP.

There is a limit to how far civil engineering can enhance road capacity in urban areas, faced with an ever-increasing number of vehicles. A congestion toll by ERP helps to price roads as scarce commodities and therefore promotes their efficient use, besides being more cost-effective than a 'manual toll plaza', or series of toll booths, where motorists have to stop and pay. The Singapore system has several advantages: there is no need for vehicles to stop or slow down as they pass the gantry; it lets large numbers of vehicles through; it allows toll charges to be incorporated based on the vehicle class; and it eliminates cash handling, thus enhancing commuter convenience and revenue security.

For expressways and approach routes leading to the city, a tiered pricing scheme operates during the peak period from 7.30 a.m. to 9.30 a.m. on weekdays. For roads in the central business district, another pricing scheme operates from 7.30 a.m. to 7 p.m. The system has allowed various pricing schemes to be tested, so that optimal speed levels are achieved on expressways (45–65 km per hour) and roads in the central business district (20–30 km per hour) by reducing the number of vehicles using tolled roads during peak hours.

Unlike the previous system, under which daily or monthly permits allowed an unlimited number of journeys, the present pay-per-trip mechanism discourages extra car use. The system motivates drivers to try quieter roads, use public transport or car-sharing schemes, and drive in off-peak periods where possible. The ERP experiment is currently being monitored before extending it to more freeways in Singapore.