I saw in the Occupations thread that we have at least one traffic engineer amongst us, so I thought I'd toss this out 'cause it's been bugging me and I have this insane need to know everything.
What is involved with converting a lighted intersection from a strictly time basis (e.g., one minute for this direction, then one minute for that direction, regardless of traffic) to one that employs sensors and switches the lights as required (or in conjunction with a timing scheme)?
I ask because a city near me has many intersections that operate on the simple time basis. No sensors. I'm not talking about the lights along the main drag that are timed with each other to allow decent traffic flow, but rather the more isolated intersections where cars end up waiting ... and waiting ... and waiting, for no good traffic-engineering reason that I can see. Lots idling engines polluting the air. Lots of gas burning.
So, is it a big deal? Expensive? Complicated? Other issues, such as reliability? I know it depends on many things, but I'd like a feel for the problem.