In article >,
Scott en Aztlán <newsgroup> wrote:
>In modern traffic sontrol systems, timers are used primarily to limit
>the maximum amount of time a particular direction will get the green
>during any particular cycle. The logic is something like
>
>while (traffic_detected AND timer < 2 minutes)
>{
> DisplayGreenLight();
>}

In NorCal, the typical traffic light control has a "default green" on
the larger street. At specific intervals (e.g. every 30 seconds, or
1 minute, or on some other schedule based on synchronization with nearby
lights on the larger street), the side street's and left turn lanes'
sensors are polled. If something is detected, the side street and/or
left turn lanes are given green. If not, the larger street continues
to stay green (or one side may stay green if only one left turn lane
sensor detects something).

Racing for the sensor won't help if you are on the "default green"
direction, but may help if you are on a side street or left turn lane
and it didn't just turn red (if it just turned red, you'll be waiting
a full cycle, so there is no point in racing for the sensor).
Observation of other traffic in the intersection can give clues as to
what phase the light is in. Though if you travel the same roads every
day, you'll probably notice a pattern that you'll always get green at
certain lights, often get red at certain other lights unless there is
no cross traffic, etc..

--
------------------------------------------------------------------------
Timothy J. Lee
Unsolicited bulk or commercial email is not welcome.
No warranty of any kind is provided with this message.