Free 'smart' devices are fitted to each car

If there is insufficient credit on a card, a camera on the gantry photographs the owner who is then fined.

The new hi-tech scheme is highly flexible - prices can be changed daily or even within the course of a rush hour - and relatively low-cost as there is no need for manned toll booths.

At the moment the toll is only levied during the rush hour in the hope that drivers will stagger their journeys or use the toll-free minor roads. Land is scarce on this tiny island and building more roads is not an option.

When your cash card runs out, a camera catches you on film

"Singapore is a growing society with rising levels of influence and people will naturally want to own cars," said Chin Kian Keong of the Land Transport Authority. "And with more people wanting to own cars on the road there must be a sophisticated way to limit usage."

The long-term aim is to persuade people off the roads and onto public transport, taking the lead from Zurich and Tokyo where more than 75% of journeys into the city centre are undertaken on buses or trains.

Now, other cities around the world will be keeping a close eye on the progress of Singapore's crusade to keep its traffic moving.