This report describes a study by the Transportation Research Group of Southampton University for the Transport and Road Research Laboratory (TRRL) concerning the obscuration of a driver's view of a traffic sign or signal by large vehicles in traffic flow. The principal area of research was an investigation of the extent to which drivers are obscured on: (a) urban multi-lane roads; and (b) rural three lane motorways. This work continued on from earlier research concerning obscuration on rural dual carriageway roads (see IRRD 818012) and used the same method of approach. This was to conduct surveys of obscuration at selected sites by setting up a video camera at the side of and over the carriageway where a sign could be mounted and making video recordings of the approaching traffic. The levels of obscuration were then assessed from the recordings by measurement of the time that each driver's head was obscured from the camera view while travelling through the viewing zone. At each site data were also obtained of the flow of heavy and light vehicles and the speed of vehicles in each lane, as well as the curvature and gradient of the approach. The results of the work from five urban road sites and five rural three lane motorways are presented in this report.

Want to know more about this project?