Archive for February 12th, 2011

February 12, 2011

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.

February 12, 2011

Car pools

My German friends, when they come over, or rather if they come over, always find our Californian car pool lanes amazing.  After I explain to them what it is, of course, because the associations connected with “car pools” are all over the place and mostly off the mark.

The beauty of car pool lanes during a bad commute, pic: mwcog.org

Car pool lanes were invented to incentivize people to commute together, to share a car, save energy, and held avoid completely congested roads.  So during commute hours, from 6 t0 9 in the morning (yes, some people drive to work that early – or so the story goes) and from 3 to 7 pm on many freeways one lane is reserved for vehicles with 2 or more occupants (pets don’t count, nor does livestock – to the best of my knowledge).

Since these cars are few and far between the car pool lanes generally allow for faster driving than the regular lanes.  A big advantage if you say, drive south on 101 and end up in the usual traffic jam around Palo Alto every day of your professional live.

Not big enough, though, for most people to drive a big detour in the morning and evening to pick up a colleague who works at the same company or nearby.  I guess, that’s why it works.  If there were too many car pools the whole thing would become counterproductive.

Just to avoid problems: it is a bad idea to take the car pool lane alone.  If they get you, you pay – though the nose.