Metering lights

This is another of those Californian traffic things that a lot of people – foreigners and those from other parts of the US – don’t know: metering lights.  Like car pool lanes, metering lights are used to regulate the traffic on freeways.  In the case of car pool lanes once the cars are already on the freeway.  The metering lights regulate how fast cars get on the freeway.

Metering lights - improving traffic flow. Hopefully. Pic: sfexaminer.com

These lights are to be found on many freeway entrances and they only have two settings: red (mostly) and green (occasionally).  The cars that want to enter the freeway stop at the red metering light and wait for green.  Unlike the usual traffic lights the green phase is very short and only one car is allowed to go per green.

This way the flux of additional cars onto the already congested freeway is limited.  Metering lights are only in use when traffic is heavy.

Of course, metering lights can be combined with with car pool lanes: cars on the car pool lane get more frequent green periods than regular cars, but still only one car is allowed.  Here is a short article about the effect of metering lights on traffic flow.

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