Adjustment of freeway ramp metering rates to balance entrance ramp queues.

In the freeway ramp metering system the variables which can be controlled are the entrance ramp rates. In order to avoid congestion on the freeway the ramp rates should be kept below critical levels. In order to control queue buildup, it is necessary to control the difference between demands and ramp rates. Since demands are uncontrollable, this implies that ramp rates should be kept as high as possible to limit queues.