Months of testing in every kind of tropical weather preceded the launch of the world's first Electronic Road Pricing (ERP) system, at a cost of Singapore $200 million (US$112 million).

The use of cars is discouraged in the tiny island state, where traffic jams would rapidly overwhelm the public facilities, and Singapore uses a system of tolls and permits to control the number of cars in its streets.

ERP eliminates the need for motorists to buy a monthly pass to enter the central business district or cruise main highways. Instead, vehicles are fitted with a smart card installed in a device on the dashboard.

Electronic devices, mounted on gantries above the road, deduct the appropriate charge as the cars pass under them.

The old pass cost the ordinary motorist S$60 a month or S$2 to S$3 a day, depending on the destinationand timing of the journey. Motorists with no passes faced fines of up to S$70.

The new system will cost between 10 Singapore cents and S$3 each time an ordinary car enters the business district or moves onto a highway.

A consortium led by Philips Singapore, a unit of Philips Electronics NV, built the new system to the government's specification, with an accuracy of one error in 100,000 transactions.

It went into action on two main highways early this month.

There have been no reports of problems on those roads, but the government had to apologise last week after 1,500 motorists were charged when workers carrying out an overnight test forgot to switch off a gantry.

For motorists, there's no escape from the ERP.

Each gantry can read the unique number of every wind screen unit, thusidentifying car and owner, and whether it has a card in it or not. A missing card means a fine of up to S$70.

The ERP seems likely to be accepted a lot more easily than the old system introduced in 1975. But there is some grumbling, nevertheless.

One taxi driver pointed to the list of rates varying from 15 Singapore cents to S$1, Which the ERP will charge depending on destination and time of day.

``Who's going to be able to remember all that? Still, we'll be passing the charge on to the passenger, so I suppose it doesn't matter much,'' he said.

Singaporeans have got used to the idea that owning a car is expensive. Besides paying for a car, they must also pay for the licence to own and use it, known as a certificate of entitlement (COE).