Congestion charging: a variety of automated toll systems are up and running.
Road-charging schemes can ease congestion and raise revenues for road maintenance, but they tend to generate controversy, particularly if they do not appear to work efficiently or fairly.
Traditional toll booth systems are crude and can cause hold-ups as vehicles queue to pay. An automated approach where drivers are charged invisibly works better and, it is argued, is fairer for road users as the distance they have travelled is measured and charged more accurately.
The technology used in such schemes falls into two camps. Older systems, such as those in Melbourne, Oslo, Singapore and Toronto, use DSRC (directional short range communications) which work through microwave or infrared technology. Drivers fit a radio tag behind their windscreens which emits a signal picked up by roadside beacons or overhead gantries.
The information is passed to a processing system which bills the vehicle for the journey. A network of video cameras is designed to catch non-payers.
London, the largest congestion charging system in the world, does not use radio tags, although it maintains a cordon of cameras at the edge of the city's central zone.
Phil Jeanes, a senior consultant with the PA Consulting Group, says no radio tags makes the London scheme "very simple. It has a flat charge and is easy to arrange." But the drawback is that it is not scaleable. There is just one charge within that area.
No such issues exist for the second type of charging technology based on GPS (global positioning system) satellites working in combination with GPRS (general packet radio service), the digital mobile phone network that is increasingly prevalent.
The distance a vehicle has travelled is measured by the satellite and sent to the driver's on-board unit, or OBU, which calculates the charge and sends it via the phone network for processing.
The first commercial system using GPS/GPRS is due to be launched in Germany for heavy trucks at the start of November by Toll Collect, a consortium of local vehicle manufacturer DaimlerChrysler, the country's incumbent telecoms carrier Deutsche Telekom and Cofiroute, which runs toll systems in France.
Experts argue that the major attraction of GPS/ GPRS over DSRC is cost. A radio tag system needs its network of roadside beacons and cameras to act as its eyes. But the cost of deployment rises as the network grows and becomes more effective. The investment for GPS - beyond transponder space on a satellite - is less significant.
A satellite-based system is also fairer, says Ian Catling, a partner in consultancy ICC, which advises on transport technology: "There's no longer a restriction to charging only at certain points. Instead you can charge by distance and time of day, allowing systems to be flexible and targeted."
The only downside, experts admit, is the cost of the OBU. In theory, this should be borne by the user, a surefire way to generate hostility among drivers. Germany's Toll Collect has avoided this pitfall by subsidising the OBU, but took delivery of too few units and had to delay its launch, amid vocal criticism.
Most road-charging schemes generate some kind of opposition. "Melbourne had no history of toll charging. It was a life-step change. There was a lot of debate whether it was a good thing, or a bad thing. Those are the issues with a high-profile project," acknowledges Brendan Bourke, chief executive of Transurban, the company that built and operates Melbourne's CityLink, launched in 2000.
Nothing stirs controversy among drivers quite as much as the perception that some people get away with not paying.
In schemes which rely on video cameras for enforcement, tampering with or disguising a vehicle's numberplate, a tactic known as cloning, is favoured by non-payers. Toll operators claim the practice is not common. Mr Bourke of Transurban says "violators" represent less than 1 per cent of transactions.
However GPS/GPRS systems are even less prone to disruption, says Mr Jeanes at PA. But even with GPS, some evasive tactics are possible. A driver could shield their OBU so that it does not give off its position. A response to that from the authorities in Switzerland was to fit all trucks with a vibration sensor, so even if the toll system in the cab is disabled the movement of the vehicle itself is still detected.
The relative security of GPS/GPRS will be reassuring for the European Commission, which has backed it as the standard for road-charging across member states.
Every existing road-charging scheme in the European Union must switch over to it by 2012, although there may be some waivers. Either way, road charging is likely to become increasingly prevalent.
One sign of its future direction was the Dutch government's 2001 proposal for every vehicle in the Netherlands, cars as well as trucks, to carry tolling technology. The idea failed to reach fruition because the government fell, but experts believe it might have a future in other countries.
"The scheme would have a tremendous impact on individuals, but also financial implications for how revenue charges are made for road usage," explains Cees de Wijs, director wireless enterprise offerings with IT supplier Logica CMG, which was involved with the Dutch scheme.
In theory, when everyone pays for actual usage then road taxes would become a less relevant means of raising revenue.
On the other hand, the scheme that was introduced in California in 1995 has become a legend in road-charging circles. Two lanes of the state's SR91 highway are free, while the other two are charged for. Motorists all carry tags and can switch lanes at will.
Backers argue the system is self-regulating - if the free lanes are crowded then drivers move across into the pay-lanes. When those become clogged then drivers switch back. "So far it's a one-off but a lot of people are interested," says Mr Catling. Certainly the element of free choice is a plus, not least with politicians who might see it as a less painful way of introducing road charging.
