Freeway congestion, ramp metering, and tolls

California freeway travelers suffer large and variable congestion delay. The delay is due to operational inefficiency, excess demand, and unforseen events. Operational inefficiency reduces speed and may cause queue spillovers that reduce exiting flows. Excess demand creates delay on ramps. Unforseen events such as accidents temporarily reduce capacity. The Cell Transmission Model of a freeway with multiple origins and destinations exhibits the spatial propagation of congestion that conforms to observations. The model is used to compare four schemes to reduce congestion in a three-lane freeway: (R) ramp control only; (T) one lane is tolled and ramps are uncontrolled; (B) bottlenecks are tolled and ramps are uncontrolled; (RB) ramps are controlled and bottlenecks are tolled. In the base case no ramps are metered and there are no tolls. It is found that (T) is inefficient and likely to leave all travelers worse off than in the base case; (R), (B) and (RB) can achieve efficient freeway utilization; (B) can eliminate queues, but has adverse spatial and equity side effects; (BR) minimizes these side effects. (BR) is likely to be much less costly to implement and maintain than (T) or (B).