Quote:
Originally Posted by CTRider
The rated speed was 55. The intersection in question had a 2 second yellow while the rest of the lights down the line had 5 sconds. The left turn arrow had a 1.5 yellow and only a 7 second green.
I seem to think it was 20/20 on ABC, so you can't blame NBC's Dateline for fudging things.
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I don't have any more faith in ABC than NBC.
At that size intersection, 4.5 to 5 seconds would indeed be within standards, but like I said... on a modern solid state controller (and any controller made since 1980), it is impossible to program less than 3 seconds of yellow. The controller software will not accept the entry.
The old electro-mechanical units designed in the 1930s? Sure... you can adjust the pins to do anything you'd like.
The short green time is another story. A typical minimum green will be anywhere from 2 to 4 seconds. Max green will be dictated by the coordination cycle time. With a 55mph limit and 8 lanes, there is going to be a lot of time needed out of that cycle for the through movements, so the engineer has two options.... run a longer cycle time, which increases delays for people on the side street, or take the time away from the left turns and the side streets. 7-10 seconds is a very common max green for a low-volume left turn.
If only one or two cars are present, the controller will only time the minimum green. Additional cars in the queue will trigger extension time that will hold the green until the timer reaches the max green.
If the signal was timing 7 seconds on that left turn no matter how many vehicles were waiting, then it's possible that it was an electromechanical unit with no vehicle detection system.