Optimal control of freeways via speed signalling1

The problem of monitoring and regulating the freeway traffic flow to increase safety and efficiency is commonly considered to be a difficult task. In this paper, a variable speed signal-based control strategy is presented to solve an optimal control problem. The freeway traffic behaviour is described by means of a macroscopic model and the effects of the variable speed signalling are modelled with the introduction of suitable parameters. An optimal control problem over a finite-time horizon is stated with the aim of reducing the probability of freeway congestion. A suboptimal solution is found based on an on-off control logic, which depends on some switching parameters to be chosen.