Effects of on-ramp and off-ramp metering on queue forming in urban traffic networks

To control the traffic flows near on-ramps and off-ramps, ramp metering installations can be used. We compare on-ramp metering and off-ramp metering, with respect to queue forming and total time spent. Both control measures are used to improve traffic flow on freeways, and both have influence on the route choice of the drivers. Although the two measures are very similar, there are some major differences. The use of ramp metering installations can change the traffic assignment in the network because the inflows or outflows of the freeways are limited. This will result in a change in travel times in the network. And since drivers make a route choice based on these travel times, the route choice (and thus the traffic assignment) can change as well. This can lead to a relocation of queues in the network. With a case study we illustrate the differences between on-ramp and off-ramp metering, with three different control methods: fixed time control, ALINEA and a model predictive control-based method.