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Old 10-22-2014, 02:39 PM
 
409 posts, read 388,981 times
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You are driving down the road and seemingly get stuck at every red light along the way. While sitting idle at yet another red light, you ponder why the traffic signals seem to be timed so poorly. It almost feels like the signals are targeting you and switch to red just as your vehicle approaches the intersection.

Any thoughts?
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Old 10-22-2014, 02:48 PM
 
409 posts, read 388,981 times
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"RED LIGHTS THAT NEVER END"
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Old 10-22-2014, 05:25 PM
 
Location: M I N N E S O T A
14,800 posts, read 17,713,305 times
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Some streets in Manhattan actually time it so if you go 30 mph you can hit almost every green light on the street you are on.


https://www.youtube.com/watch?v=KLo3fJSqotw
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Old 10-22-2014, 05:43 PM
 
Location: Atlanta
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Oh gosh, I hate stoplights more than anything. They're the bane of every city in the world.

That's one thing I'm gonna love about the UP of Michigan when I eventually move up there - very few stoplights.
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Old 10-22-2014, 06:22 PM
 
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Sometimes if you run one, or at least push the yellow, you get green on the rest. It's like a reward for doing wrong.
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Old 10-22-2014, 10:05 PM
 
409 posts, read 388,981 times
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Bell Road is a busy arterial that services suburban Phoenix. Major intersections are spaced 0.5 miles apart and has a speed limit of 45 mph (a typical suburban arterial setup). Below are time-space diagrams for Bell Road running various cycle lengths optimized to reduce delay:

Bell Road (80 second cycle):


Bell Road (120 second cycle):



Time-space diagrams are useful in visualizing traffic flow along a roadway. A horizontal line in the time-space diagram represents vehicles that are stopped (IE. waiting at a red light). Good signal progression is achieved when Bell Road is running an 80 second cycle. If the traffic signals were timed for an 80 second cycle, it would reduce the amount of red lights drivers get stopped at. Simple! There are some problems though:

1. Wide arterials lead to long pedestrian crosswalks (there is a 130 ft pedestrian crosswalk at Bell Rd & 7th Avenue). To ensure that pedestrians have enough time to safely cross the street, the total cycle length needs to be lengthened. Quite simply, an 80 second cycle wouldn’t be long enough to fit the required pedestrian times.

2. The major signals along Bell Road are 4-phased signals with dedicated left turn phases. As the number of signal phases increases, higher cycle lengths are needed to account for the associated "lost time" each phase adds. Quite simply, an 80 second cycle doesn’t operate very efficiently at busy 4-phase traffic signals.

What's the end result? You’re stuck running a 120 second cycle length which leads to poor signal progression. Bell Road is a good example of why it’s so difficult to achieve good signal progression along suburban arterials.
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Old 10-23-2014, 09:32 AM
 
Location: East Mt Airy, Philadelphia
1,020 posts, read 1,037,999 times
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Quote:
Originally Posted by iNviNciBL3 View Post
Some streets in Manhattan actually time it so if you go 30 mph you can hit almost every green light on the street you are on.


https://www.youtube.com/watch?v=KLo3fJSqotw
I grew up (and learned to drive) in NJ, just outside Manhattan. One of the pieces of advice my father gave me the first time I drove in Manhattan was to drive at some speed (maybe 30? I think there are a couple of speeds) so I "hit the greens." I followed his advice and the results weren't as spectacular as the video that's linked here, but it was kind of magical (and, I believe, never repeated).

Also, when my wife and I moved from Chapel Hill NC to Philly, the last time we drove from our house to I85 we had to go, as always, along US15-501. This is a corridor that grew increasingly crowded during the many years we lived in the area. You could rely on it being stop and go, and would always allow extra time when using it. This last time, though, we hit nothing but greens, almost as if the town was saying "yeah, good riddance. See how Philly works out for you. It'll be nothing but reds when you come crawling back."
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Old 10-31-2014, 04:35 PM
 
5,721 posts, read 5,466,236 times
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Quote:
Originally Posted by impala096 View Post
You are driving down the road and seemingly get stuck at every red light along the way. While sitting idle at yet another red light, you ponder why the traffic signals seem to be timed so poorly. It almost feels like the signals are targeting you and switch to red just as your vehicle approaches the intersection.

Any thoughts?
I prefer to coast to red lights. If I see one in the distance I take my foot off the gas, so by the time I get there, it's green and I don't have to use the brake at all. But if you're close to it, there is often no way to avoid the red light. It would be nice if they put a timer to show when a light was going to change so you could plan accordingly. It would improve my gas mileage.
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Old 10-31-2014, 05:20 PM
 
409 posts, read 388,981 times
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Quote:
Originally Posted by juppiter View Post
I prefer to coast to red lights. If I see one in the distance I take my foot off the gas, so by the time I get there, it's green and I don't have to use the brake at all. But if you're close to it, there is often no way to avoid the red light. It would be nice if they put a timer to show when a light was going to change so you could plan accordingly. It would improve my gas mileage.
Here's an example of a traffic signal "talking" to an approaching vehicle. The time left in the phase can be displayed directly in the vehicle's center console. This V2I test bed is on Telegraph Road in metro Detroit.


https://www.youtube.com/watch?v=R02SmHKy1ic#t=130
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Old 11-01-2014, 11:37 AM
 
409 posts, read 388,981 times
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Speaking of Telegraph, it's one of the few roads where drivers can go several miles without getting stuck at a red light.

https://www.youtube.com/watch?v=7hvUm9vYJYI
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