Providers of tolling enforcement systems frequently use equipment which is operational over a width less than a full carriageway and use multiple beams to cover the width required. This inevitably results in a non-uniform lateral profile. As a result, equipment aligned to cover the centre of motorway lanes may be less efficient at lane edges. TRL was commissioned to investigate and report on the lateral distribution of vehicles across motorway carriageways under a range of typical conditions. The preferred option of analysis was that of video tapes from existing archive material of motorway scenes. The results obtained suggested that different patterns of lateral displacement distribution exist for different scenarios. The main differences occurred at sites where there is a gradient, a lay-by, significantly more lane-changing, different flow and speed conditions, and where there is a mix of traffic. The lateral displacement of vehicles appear to be most affected by the proportion of HGVs and the speed of traffic. (A) (This report is also included on the TRL CD-ROM entitled "Research on road user charging 1995-1998"). For the covering abstract see IRRD 491340.

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