This article describes the technology used in multi-lane electronic toll collection systems, with particular reference to the Norwegian Q-Free system. Multi-lane systems must be reliable and effective without requiring barriers to traffic flow. Two outcomes to avoid are a vehicle passing without payment and incorrect enforcement. The overall system architecture comprises a set of subsystems with dedicated tasks for handling passing on-board units and vehicles. Co-ordination between the subsystems is essential. Data transmission is by dedicated short-range communications: the Q-Free system is compatible with several charging protocols in Europe and elsewhere. Detection and classification of vehicles must be highly accurate: sensor systems operate with cameras using infrared technology for licence plate recognition even in low light conditions. For the covering abstract see ITRD E118381.
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