Design and assessment of in-vehicle interfaces for electronic toll collection.

Electronic Toll Collection typically involves `tags' or On-Board Units (OBU) which can inform the driver of tolling transactions and credit balance. As part of the technology trials undertaken on behalf of the UK Department of Transport, TRL has undertaken an assessment of the usability and safety of several OBUs. The user needs, and hence required OBU functionality, depend to a large extent on the characteristics of the whole tolling system, including `back end' financial aspects. Thus, while it is not possible to assess an OBU in isolation from its infrastructure or to define an `ideal' unit, overall requirements and design guidelines to achieve a desired functionality can be proposed. (A)