Better traffic flow at highway ramps with help of mathematics

Mathematical coordination of traffic control measures at highway ramps leads to a better traffic flow.

Publication date: 23-11-2012

Mathematical coordination of traffic control measures at highway ramps leads to a better traffic flow. This is one of the conclusions of researcher Pia Kempker - PhD student at the Vrije Universiteit Amsterdam and the Centrum Wiskunde & Informatica (CWI) in Amsterdam. She defends her PhD thesis ‘Coordination Control of Linear Systems’ at the VU on 23 November.

If different systems have to fulfill a task together, they often need some kind of coordination. Take, for example, a game of robot soccer where several autonomous robots must cooperate to win, or think of several trains on one track that must adapt their speed to each other. For some applications, a hierarchical control of decentralized modules is best, which limits the communication and therefore the costs. To describe this hierarchical control, Pia Kempker formalized, amongst others, with mathematical techniques the concept of 'a system that is as decentralized as possible’. Her results provide insight into the sometimes complex structure of large linear systems and allow for a decentralized approach.

Kempker describes two applications of the mathematical results: formations of autonomous underwater vehicles and - the earlier mentioned - coordination of the influx of traffic from neighboring highway ramps. If too much traffic tries to enter the highway, the ramp metering leads to waiting queues at the driveway. In the case of local influx control, the waiting queues can vary widely for neighboring highway ramps - an unwanted effect that coordination can prevent. Coordination creates a fairer distribution of the ramp metering. In the other example the hierarchical approach is also efficient. This research was funded by the EU C4C project.

More information:
Supervisors: Prof. J.H. van Schuppen en Prof. dr. A.C.M. Ran
See also: http://www.vu.nl/nl/nieuws-agenda/agenda/2012/okt-dec/23-november-p-l-kempker.asp
An earlier news item on the C4C project: http://www.cwi.nl/news/2011/motorway-traffic-control-benefits-eu-c4c-project  
Picture: Ramp metering - by Jan van Schuppen, November 2011