Washington, D.C., and Minnesota have control designed to maximize bottleneck flows with section-wide explicit coordination, an approach Los Angeles is also adopting in a system currently under development. Simulation analysis showed that the Minnesota approach distributed traffic flows more evenly on the mainline, but had more ramps with higher waiting times than the other approaches.
Long trips benefit from metering at the expense of short trips.
A limit on individual delay, even at the expense of overall freeway efficiency, may be necessary for the ramp metering system to satisfy equity considerations. Ramp simulation Panos Michalopoulos's goals were to develop a simulation lab and implement this evaluation methodology on two freeway segments in the Twin Cities. The implementation of ramp metering should be site and time specific. However, there were adverse effects on the ramps themselves, including queues and delays. Simulation will allow new strategies to be tested and existing ones to be fine-tuned before deployment.