Technologies & impacts
Currently, several technologies are used or have been considered for charging:
satellite navigation system to locate the vehicle
Dedicated Short Range Communications, for two-way communication between a roadside or gantry beacon and in-vehicle tags or transponders.
video-based license-palte recognition, using roadside cameras with automatic optical character recognition software to match vehicles' number plates with a preregistered list
Most of the existing RUC schemes are based on DSRC. Nevertheless, this technology requires important investments in roadside infrastructures. One of the main advantages that GNSS has over DSRC is the ability to cover a much greater road network without expensive infrastructure costs.
All GNSS-based systems to date have necessarily used GPS as the satellite location system. However, it is recognised that navigation with GPS faces a number of limitations, concerning in particular the lack of guarantee of the location accuracy because there is no guarantee of the signal integrity. This is of particular relevance in urban environments where signal obstruction by features such as tall buildings, urban canyons, bridges and trees, as well as the effects of multipath caused by signal reflections from buildings and other vehicles raise many problems. As a consequence, there exist major risks for overcharging (at the expense of the driver) or mischarging (at the expense of the road operator)
With the advent of the European system EGNOS, this integrity problem is now overcome. Moreover, the introduction of Galileo in 2013 will also increase the overall performance of the system.
Figure: concept of integrity