Congestion, ramp metering and tolls.

The cell transmission model of a freeway is used to compare four congestion-reducing schemes: (R) ramp control only; (T) one lane is tolled and ramps are uncontrolled; (B) bottlenecks are tolled and ramps are uncontrolled; and (RB) ramps are controlled and bottlenecks are tolled. In the base case, ramps are uncontrolled and there are no tolls. It is found that (T) is inefficient and may leave all travellers worse off; (R), (B) and (RB) can achieve efficient freeway use; (B) can eliminate queues, but has adverse spatial and equity side effects; (RB) minimizes these side effects. (RB) is likely to be least costly to implement and maintain.