Light timing: who is responsible?

[Kodak]

Are urban planners responsible for traffic light timing, or are there specific traffic engineers who make a living trying to decided how to route traffic?

[gone-ot]

...around HERE (Tucson, AZ) apparently nobody. Timing seems to be a total "after-thought" that gets attention only after some business complains about a light not letting its customers enter/exit quickly enough...all other (drivers) inputs seem to be 'circular filed.'

[Diesel_Dave]

Originally Posted by Kodak

Are urban planners responsible for traffic light timing, or are there specific traffic engineers who make a living trying to decided how to route traffic?

Interesting question. I would like to know the answer to that question as well. Much of my route is on rural highway. There are a few red lights at intersections. Since they're in a rural area, I'm sure there's no "urban planner" involved. If I had to guess, they were set up once when thye put in the red light and never touched again. So my guess is it would be whoever the DOT contracted to install it.

Most of the ones I go through are not "timed" per se--they have sensor loops and I assume by observations that there's a "sensitivity" adjustment that determines how much of a gap in traffic cross-wise is required to transition as well as a "time-out" adjustment, where it will eventually transition (in heavy or no traffic).

[some_other_dave]

Originally Posted by Kodak

Are urban planners responsible for traffic light timing, or are there specific traffic engineers who make a living trying to decided how to route traffic?

I'm pretty sure it depends on the location, who installs and "owns" the light, etc. I know that there are traffic engineers who make a living working out traffic routings and such, but I'm pretty sure they don't work everywhere.

Many lights don't seem to be timed at all. Others are obviously connected to other lights. Still others are "locally" controlled by magnetic induction loops in the road.

-soD

[tru]

Transportation engineers working for DOT or contractors for DOT are responsible for timing based on traffic flow and traffic studies. transportation engineers fall under the civil engineering discipline... for the most part red and yellow times are mathematical based on reaction time, intersection length, and the speed limit. green time varies based on the traffic studies presented at the time the lights were installed and sometimes projected future growth.

That being said the use of sensors in the road and cameras can adjust green times for specific times of day to make the lights more driver friendly. The biggest problem IMO is the lack of continuity between intersections, each one typically acts as its own entity. Engineers recognize this and will attempt to design streets with a "green wave". Once a driver hits one light, the remaining lights on that route will be green, if the driver continues at the posted speed limit. I'd like to go on further but i dont think its necessary.