Optimisation of motorway operations via ramp metering and variable speed limits

Abstract

This paper presents a modelling and optimisation framework for deriving ramp metering and variable speed control strategies. We formulate the optimal control problems aiming to minimise the travel delay on motorways based upon a macroscopic cell transmission model of traffic. The optimal ramp metering optimisation is formulated as a linear programming (LP) while the variable speed control problem is formulated as a mixed integer LP. The optimisation models are applied to a real scenario over a section of M25 motorway in the UK. This paper also includes various analyses on the sensitivity of the optimal control solutions with respect to different network configurations and model assumptions.

Keywords:

• cell transmission model
• mixed integer linear programming
• ramp metering
• variable speed limits

Acknowledgements

The authors would like to thank the comments from the anonymous referees. We would also like to acknowledge the UK Highways Agency for providing the MIDAS traffic data and IBM Academic Initiative for providing the software and license for using the CPLEX Optimisation Studio.