With continued increases in traffic demand, congestion is now recurring on many sections of the UK motorway network in peak periods. This paper describes a large UK study undertaken by the University of Southampton for the UK Transport Research Laboratory aimed at understanding and predicting motorway capacity and the flow breakdown phenomenon. Such an understanding of fundamental parameters is clearly of importance if possible improvement measures are to be assessed and prioritised. The study was based on the video-based collection, compilation and statistical analysis of a large traffic database covering flows, composition, speeds, densities, headways and lane changing at some fourteen motorway sections suffering from recurrent congestion. The paper summarises the results of the study including predictions of motorway capacity, merge capacity and flow breakdown occurrence. The paper concludes with a discussion of committed proposed improvements to motorway operations in the UK, including motorway widening, motorway tolling, traffic management and control, and new advanced information systems. (A)
Abstract