Optimal motorway traffic flow control involving variable speed limits and ramp meteringOptimal motorway traffic flow control involving variable speed limits and ramp metering Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2015-10-232010enThe impact of variable speed limits (VSL) on aggregate traffic flow behaviour on motorways is shown to bear similarities to the impact of ramp metering, in particular, when addressing potentially active bottlenecks. A quantitative model of the VSL impact is proposed that allows for VSL to be incorporated in a macroscopic second-order traffic flow model as an additional control component. The integrated motorway network traffic control problem involving ramp metering and VSL control measures is formulated as a constrained discrete-time optimal control problem and is solved efficiently even for large-scale networks by a suitable feasible direction algorithm. An illustrative example of a hypothetical motorway stretch is investigated under different control scenarios, and it is shown that traffic flow efficiency can be substantially improved when VSL control measures are used, particularly in integration with coordinated ramp metering.http://creativecommons.org/licenses/by/4.0/Transportation Science442238 - 253 Rodrigo C. Carlson Ioannis Papamichail Papageorgiou Markos Παπαγεωργιου Μαρκος Albert Messmer INFORMS