r/phoenix • u/bryanskee808 • 1d ago
Commuting Traffic light timing
How is the timing on traffic lights spot on for speed limit driving? Going anything faster you’re just rushing to wait. North Phx and North Scottsdale area. You’d have to excessively speed to beat the lights.
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u/get-a-mac Phoenix 1d ago
Look up the fiber network behind all of this called the Maricopa county regional community network (RCN) and ITS, it’s pretty advanced cool stuff.
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u/babj615 1d ago
Where in Phoenix do you find optimized traffic light timing?
Catching a red light while traveling north or south on Scottsdale rd or Cave Creek rd always results in a 'Red Light Relay' where you can't possibly make any of the lights before they turn red.
Many other major corridors are the same way.
Traffic control in Phoenix is horrible!
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u/Fongernator 1d ago
When I used to live near downtown you could go up 7th Street on a Sunday morning going around the speed limit from McDowell to northern without stopping.
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u/fluffhead79 20h ago
What pisses me off is why they don't use asphalt sensors at the smaller intersections. There is no reason to sit at a light for a minute and half with zero traffic there. I'm looking at you central Phoenix. It's stupid.
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u/zx9001 Peoria 5h ago
They probably do, the sensors are just broken. Broken sensors default to assuming the maximum level of traffic on all sides. Broken sensors often go go unfixed because most people dont even notice, most of the few that do assume it's intentional, and most of the rest can't be bothered to report it.
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u/earth_quack 17h ago
I can say the lights in west PHX and Glendale are optimized to prevent the flow of traffic. The half streets sometimes change every 15 seconds during rush hour. Some lights turn yellow and then back to green which really messes things up. The traffic lights near the light rail in certain areas turn red for the train that's not even there. I've submitted dozens of traffic control tickets but gave up because nothing ever gets fixed.
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u/bear45188721 23h ago
I used to drive Shea Blvd from 101 to 87 and believe it or not if I caught the first green light and stayed at about 47 mph ( I know the limit is 50) I caught all greens to Fountain Hills. But that was a long time ago and traffic is way worse now.
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u/Ok_Subject_7458 1d ago
everyday same cars on the same road. speed pass me just to meet me at the next light. its like do you people never learn?
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u/girrrrrrr2 1d ago
They are hoping to be able to skip one light and then it’s all totally worth the increased risky behavior!
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u/OneManGang2001 1d ago
It baffles me when approaching a red light with 20+ vehicles stopped in ach lane blow past me from a tad away only to slam on their brakes to stopped cars.
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u/Ice_Sinks Scottsdale 14h ago
It's annoying, I recently switched jobs, old job was a right turn at the first light out of my complex, I'd get green lights the entire time. But now, my new job I have to wait at the light to make a left, and now I get caught at almost every red light every single time.
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u/version13 9h ago
In Phoenix seems pretty easy to adjust your speed to time the lights so you hit green, but in Tempe it just seems so random.
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u/Fuzzy_Technology7539 39m ago
Sensors were probably moved when alot of these cameras were being put up. Usally they're right at or barely inside the cross-walk line. If you notice, (if you csn find one anymore) cabs stop a foot or more away from this line as well as this younger generation..not that they know about the sensors, but they just don't pull up to the line. No pressure no Sensor. Ever been in turn lane and the person ahead doesn't even pull into middle? Lucky if 1 car makes a turn.
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u/MysteriousCicada5012 15h ago
Main Street in Mesa if you go 42 mph you can hit every green, might have to slow down at the light if there's a left arrow.
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u/SkyPork Phoenix 1d ago
They're timed really well sometimes. I'd even say most of the time; I imagine the metro area puts a lot of work into timing the lights to make traffic as effective and safe as possible. But there are always outliers, lights that aren't linked with the other lights, or whatever. I've been going along, enjoying the nice flow of the lights, and then one light that only controls the entrance to a fucking strip mall will stop me, and throw off the rest of my drive, and I'll think, "you know, if I'd been going 5mph faster, I'd have made it...."
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u/Glendale0839 1d ago
As someone who drives a lot on the east-west avenues in Glendale and Peoria during rush hour, my biggest complaint is that it seems no thought was put into tailoring the light timing to the fact that the vast majority of the traffic is eastbound in the morning rush and westbound in the evening rush. The lights change too often and stay green too long for the relatively minor amount of northbound/southbound cross traffic during those hours.
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u/zx9001 Peoria 5h ago edited 3h ago
Peoria actually defaults most of their lights to permanent green on the east/west axis in the absence of traffic. The only exceptions are 91/cactus and most of LPP (except except LPP/happy valley, where happy valley is the default green)
The issue Peoria has is that there is zero synchronization across most of its network, except for a few corridors (83/peoria from the fire station to 83/cholla, tbird from 83 to 91, maybe bell and LPP?). It runs a mostly uncoordinated network, which is fucking great if you drive off peak hours like I do. You'll usually never have to wait at an empty red light if driving overnight, unlike in Glendale, where you could be held up for up to 90s if you arrive at the wrong time.
Minor lights are also programmed to change as soon as it detects a gap in traffic, which often happens right before a line of cars is about to arrive. The light will wait for up to 10 seconds in case the vehicle wants to turn right, then for the next 50 seconds, will change if it senses a gap in traffic. After 60 total seconds, the light changes anyway. This is great for ensuring that nobody has to wait too long, but for the line of cars on the major street is really annoying. Fortunately, the minor greens are short, usually 5s minimum but a few have 10s min greens.
As for Glendale, they run a fixed grid. I notice that traffic usually flows pretty well, then comes to a dead stop at 67 av. 67 appears to be heavily prioritized N/S, as traffic on 67 is usually free flowing, at the expense of every cross street (greenway, tbird, cactus, peoria) along the way. For example, during the M-F evening timing grid (4?-10p) at 67/tbird, 67 gets 74 seconds of green vs tbird's 59s. I wonder if the decision to make 67 a priority N/S street is because of peoria's lack of a synchronization, and the fact that it's at the edge of a coordinated grid so it would have less impact overall.
Glendale's minor lights use a mix of both. They have fixed intervals at which it checks for a car, which bizarrely, use different cycle lengths than the major intersections (M-F evening unmeasured, overnight/weekend 90s vs 120s cycles). Many lights now, however, have detection systems that will immediately start counting down the crosswalk when it sees a car, rather than change instantly like many peoria lights do (peoria always keeps the crosswalk at a red hand unless manually activated or on a prefixed timer). Because apparently the walk signal must burn continuously even if nobody wants to cross the street i guess. At least its shorter than waiting for a 90s cycle.
Phoenix uses fixed 90s intervals for minor lights, but their majors also run on 90s cycles overnight, so it works really well.
I actually did a records request to get the timing data at many Peoria intersections, though it's not really useful for mapping out a grid it's still interesting to see the min/max times, which match up with my personal observations.
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u/AntAir267 1d ago
Studied this in college, there are a variety of ways to measure appropriate light timing. Most common nowadays is just companies who buy traffic data and extrapolate the ideal settings with math.
Honestly, people don't realize how many hundreds of millions of dollars it costs over time (in a car-dependent city like Phoenix) to have unoptimized traffic patterns. It costs people time they could be otherwise spending shopping or working or attending events (or any number of other things that are good for the economy.) Not to mention pollution.
It would be more economically viable to pay highway construction crews exorbitant amounts for 24/7 work than the sum of all the lost productivity caused by construction-related traffic. But we live in a world obsessed with short term thinking so that's never going to be fixed.
Fun fact, ADOT controls all the light timings on highway junctions and refuses to collaborate with cities, so now you know why those lights never sync up right.