Ramp Metering

A ramp meter, ramp signal or metering light is a device, usually a basic traffic light or a two-phase (red and green, no yellow) light together with a signal controller, that regulates the flow of traffic entering freeways according to current traffic conditions. Ramp meters are claimed to reduce congestion (increase speed and volume) on freeways by reducing demand and by breaking up platoons of cars. Two variations of demand reduction are commonly cited; one being access rate, the other diversion.
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The process of facilitating traffic flow on freeways by regulating the amount of traffic entering the freeway through the use of control devices on entrance ramps. 2) The procedure of equipping a freeway approach ramp with a metering device and traffic signal that allow the vehicles to enter the freeway at a predetermined rate. (TRB1)