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Closely-spaced traffic signals that ought to have better timing

Started by epzik8, November 18, 2017, 04:24:37 AM

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epzik8

First, apologies if this topic has already been covered. That said, I am curious to hear of any two or more traffic signals you know of in close proximity to each other that you believe should have better timing synchronization. My inspiration for this post is a pair of signals in the area of Towson, Maryland, on Route 146 at Pot Spring Road and Seminary Avenue. These lights are pretty close to one another, and it is not uncommon for one of them to be red while the other one in the same direction is green. Thus, cars who should be able to proceed because the first light is green sometimes can't because the second light is red for them.
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jeffandnicole


tradephoric

It's possible that the first signal is resting in green because there is nobody detected on the side-street whereas the second light is red because there are drivers detected on the side-street.  This scenario is pretty common and doesn't indicate poor signal synchronization.  The signals in your scenario are only about 500 feet away and it might make sense to cycle both signals when there is a side-street actuation at either signal, but then drivers may question why they are getting stopped at that first red light when nobody is waiting on the side-street.

Personally, i would rather have the first signal rest in green because if I'm a driver going the other way who just makes it through a yellow light i don't want to get unnecessarily stopped at the next light when nobody is waiting on the side-street.

mrsman

Quote from: tradephoric on November 18, 2017, 11:48:19 AM
It's possible that the first signal is resting in green because there is nobody detected on the side-street whereas the second light is red because there are drivers detected on the side-street.  This scenario is pretty common and doesn't indicate poor signal synchronization.  The signals in your scenario are only about 500 feet away and it might make sense to cycle both signals when there is a side-street actuation at either signal, but then drivers may question why they are getting stopped at that first red light when nobody is waiting on the side-street.

Personally, i would rather have the first signal rest in green because if I'm a driver going the other way who just makes it through a yellow light i don't want to get unnecessarily stopped at the next light when nobody is waiting on the side-street.

Of the two cross streets, Seminary seems to be busier than Pot Spring and it also goes both east and west of MD 146.   I would think that in a situation like this, the best thing to do would be to coordinate the signals in a way that the signal at Seminary "controls" the signal at Pot Spring.  This means that the signal at Pot Spring should have less red time (measured from the point of view of MD 146) than Seminary.  The Pot Spring signal facing MD 146 should turn red after the signal at Seminary and should become green before the signal at Seminary.  (I.e. if the travel time between the two signals is 10 seconds, and the green phase for MD 146 at Seminary is 40 seconds long, the green phase at Pot Spring should be 60 seconds long starting 10 seconds before the signal at Seminary gets green and ending 10 seconds after Seminary's signal stops being green.)

If this were well planned, you should never hit a red at Pot Spring if you hit a green at Seminary. But the reverse may not be true, since Seminary is busier than Pot Spring.



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