| Abstract |
The Department of Transport has commenced a research programme into motorway tolling technology. Traffic levels on the UK motorway network, which has a total length of over 3,200 km, are such that only full speed free flow tolling could be used. Systems for evaluation are being supplied by consortia made up of major electronic and communication companies. They will undergo trials at the Transport Research Laboratory test track in Berkshire. The presentation considers the technology which might be used and the problems to be overcome before a system could be introduced in the UK. The final system for the UK may use either closed or open tolling; a final decision has yet to be taken. But in either case the fact that the network is continuous means that it will be necessary to be able to toll the full flow of motorways, typically up to about 6,500 passenger car units (pcu) per hour on a three lane dual carriageway. An evaluation of the technology suggests that a system based on microwave communication between gantry mounted equipment and In-Vehicle Units (IVUs) mounted on the windscreen of the vehicle might be used. This would operate at 5.8 GHz, and would need to conform to the emerging standards drawn up by Technical Committee 278 of CEN, the European standards body. Payment would either be by a pre loaded smart card in the IVU or by charging to a central account. In addition to the basic transaction subsystem there is also an enforcement subsystem. If the IVU fails to make payment properly, or if there is no IVU, then the vehicle passage must be recorded for subsequent follow up action. The use of free flow tolling raises a number of issues concerned with this enforcement of violations. The first is that any individual system error due to a 'glitch' or interference in the received signals, may be indistinguishable from an attempt to evade payment. This means that the rate of such errors must be extremely low, perhaps 1 failure in 30,000 transactions or better. But even these rates would be unacceptable if every equipment error resulted in an attempt to take enforcement action. Hence there is a need for a further stage of filtering, using statistical techniques, to allow systematic attempts to evade payment to be identified and isolated from the errors due to equipment imperfections. The need to determine whether such cooperation is possible is a key element of the trials. The trials will also provide an opportunity to study the organizational aspects of the systems for consolidating payments to produce a revenue stream, for handling enforcement notices and into areas such as electro-magnetic compatibility. In principle tolling will also provide a two way data channel between the roadside and vehicle at discrete points on the network. The possibility of using this for ITS/Telematics services is also being examined. |
TRT
