Ramp and signal control: Where motorways and urban roads meet

Control schemes for motorways and urban roads are often modelled as separate systems. This may be reasonable when there is substantial buffering at on-ramps on motorways. However, in many densely populated areas, the length of these on-ramps can be limited, and traffic may easily propagate into the urban road network. We consider the problem of congestion control on a motorway and its surrounding roads. We analyse two control policies: Proportional fairness and Backpressure, which are commonplace in the modelling of communication networks. We provide an initial analysis and performance evaluation, of these control policies, in the context of joint motorway and urban traffic scheduling.