Traffic Lights Time from Green to Red

Caerdyddblue on 10/08/2022 - 12:28

Hi everyone,

Bit of a random one, is there a set timeframe that traffic light will take to change from green-amber-red and then for the opposite travelling intersection to go from red-amber-green?

I don't mean how long you spend at a set of lights, it seems like some traffic lights change from green to red and the traffic travelling across the intersection from red to green faster than other intersections? There is a newer set of lights close to my home that seem to be suspiciously fast!

Some in VIC seem to be changing to amber by the time the other is also amber. Not sure about if that's a state thing.

Automotive

Comments

  • Ozbar Gain on 10/08/2022 - 12:33
    +16

    I'm pretty sure that the speed zone and the expected amount of traffic get considered for each intersection when determining the duration the amber light get shown

    • askbargain on 10/08/2022 - 12:35
      -3

      More like the time it takes for a car to clear the intersection once they enter it.

      • Chandler on 11/08/2022 - 14:44

        Both.

        Amber long enough for an approaching vehicle to safely stop at the lights;
        Amber + (all) red long enough for a vehicle that wasn't able to stop to clear the intersection before releasing opposing traffic.

    • tight-ass on 10/08/2022 - 13:39

      Correct - it's based on the speed limit of the road

  • Xistn on 10/08/2022 - 12:36
    +2

    In Victoria, Red is the new Green.

  • holdenmg on 10/08/2022 - 12:36
    +8

    I don't recall Lights going Red, Amber, Green. Usually Red, then Green. YMMV

    • andresampras on 10/08/2022 - 12:42
      +4

      ….then how are you supposed to know when to put your car in Launch mode?

      • holdenmg on 10/08/2022 - 12:54
        +2

        Only mode I use… lol

    • LFO on 11/08/2022 - 13:42

      It is very common overseas, to indicate green is coming … get your brain into gear pleeeeease …

  • Ugly on 10/08/2022 - 12:40
    +15

    There’s a whole science behind it ! - https://www.foresitegroup.net/a-beginners-guide-to-signal-ti…

    “ The split includes the green time and the clearance interval, or the time to clear the intersection, which includes the yellow and red lights. Clearance interval times are calculated based on speed limit, intersection widths, intersection grades, perception or start-up time, and acceleration rates”

    • askbargain on 10/08/2022 - 14:04

      Amazing how people still believe the first comment instead of this.

      • [Deactivated] on 10/08/2022 - 15:14
        +2

        Your other comment, this comment and the first comment are all technically right (about some of the things taken into account) according to that link. Dunno what you think you’re arguing about when you’re all correct. Both your other comment and the first comment are incomplete answers, but you are 100% wrong when you dismissed the first comment as wrong.

        • askbargain on 10/08/2022 - 15:29
          -3

          expected amount of traffic

          Like anyone is going to use this as a metric.

          And OP’s question was when one light turns red and the other turns green, not how long a light is amber.

          • [Deactivated] on 10/08/2022 - 15:40
            +2

            @askbargain: Read OPs question again. They worded it confusingly but they asked about the whole process. Now I see why you answered less correctly though.

            Like anyone is going to use this as a metric

            According to several links in this page yes, it’s used in light timings, including the one you just responded to without reading obviously. Even your answer about clearance time has a basis in traffic volumes and is effected by them because they increase with heavy traffic lowering speeds!

            Cycle Length
            A cycle length is the amount of time required to display all phases for each direction of an intersection before returning to the starting point, or the first phase of the cycle. Cycle lengths are based on traffic volumes and work best within a certain range depending on the conditions of the intersection. The goal of signal timing is to find an optimum cycle length for the most efficiency. Typical cycle lengths may range from one minute to three minutes. A split determines how much time each movement gets in a cycle. The split includes the green time and the clearance interval, or the time to clear the intersection, which includes the yellow and red lights. Clearance interval times are calculated based on speed limit, intersection widths, intersection grades, perception or start-up time, and acceleration rates. Clearance intervals are often referred as the change interval, when changing from one signal phase to the next. The clearance time in that sequence is also referred to as “loss time” due to vehicles coming to a stop or starting-up and the time that no vehicles are moving through the intersection.

            • askbargain on 10/08/2022 - 16:29
              -2

              @[Deactivated]:

              They worded it confusingly

              change from green-amber-red and then for the opposite travelling intersection to go from red-amber-green?

              It is pretty clear he is talking about a single timing here. Maybe you need to read OP's question again.

              expected amount of traffic

              If you listened in math class, expected amount isn't what you quoted yourself above. In Victoria, where OP is from, they have metal detectors that detect when a car passes by and extends the green light time, which isn't even OP's question.

              Or to dumb it down for you, how can a traffic light expect how many cars are on the road?

  • djones145 on 10/08/2022 - 12:45

    I think you need to travel Australia and get statistics on every traffic light and timings, then write a paper on it

    buy a rolex though, the official timer for all swimming races for accurate timings!

    • andresampras on 10/08/2022 - 13:03
      +4

      OzB only recognises digital Casio models for timing

  • AndyC1 on 10/08/2022 - 13:06
    +1

    It varies depending on the speed, but there is a minimum which I have no idea.

    I slow down when the lights change to orange unless it is dangerous to do so in order to stop when the lights change to red.

  • bobbified on 10/08/2022 - 13:11
    +2

    There's this thing called the SCAT (yes, that's what it's called!) system that's used in Australia to control the timing of the traffic lights based on live traffic conditions.

    • GordonD on 10/08/2022 - 17:09
      +1

      Scat has a common meaning. It has a related meaning in music. And it has a completely different meaning in animal biology. If you are referring to the third of those, its probably gone over most peoples heads.

      • bobbified on 10/08/2022 - 17:14

        If you are referring to the third of those, its probably gone over most peoples heads.

        I dunno about that - it's the first definition in my favourite dictionary! 😋

        • GordonD on 10/08/2022 - 17:18

          Ah, make that four meanings.

  • John Kimble on 10/08/2022 - 13:22

    I'm thinking based on personal experience under 3 seconds.

    Why don't you time that intersection and then time a few other random intersections to compare?

  • JimmyF on 10/08/2022 - 13:25
    +1

    Bit of a random one, is there a set timeframe that traffic light will take to change from green-amber-red a

    No set time for how long they are 'green' or 'red', but there are time frames around how long they are amber and it is based on the road speed limit. Then it is normally all lights are 'red' for 3 seconds before one goes green.

  • cyan00FFFF on 10/08/2022 - 13:29
    +3

    There's a lot of settings in the software that can be changed to meet the needs of specific intersections.
    Reading from some old RTA documentation (NSW), the controller software allows for yellow time to be set for anything between 3s and 6.4s, with manager approval required for anything under 4s. The specific setting at each intersection is chosen based on the speed limit and whether it's a steep up/down hill grade on approach. It lists the following times as typical:
    40-60km/h: 4s
    70km/h: 4.5s
    80km/h: 5s
    90km/h: 5.5s

  • pegaxs on 10/08/2022 - 13:44

    Let me guess, you got a red light ticket and are wanting to claim that the light wasn’t yellow long enough and you couldn’t stop based on that…

    • John Kimble on 10/08/2022 - 13:57
      +1

      Nope, if I'm understanding correctly, they are asking how long it takes for the other lights to turn green if the OP's light just turned red. All that other stuff just confused everything.

      Eg if OP is travelling north-south and their light turned red, how long until the east-west lights turn green.

      Happy to be corrected.

      JimmyF thinks a 3 second period of all red. That's what I was thinking also.

      https://www.ozbargain.com.au/comment/12523674/redir

      Didn't neg you btw

    • Caerdyddblue on 10/08/2022 - 14:03
      +1

      Wrong actually but thanks for the assumption :)

      • pegaxs on 10/08/2022 - 14:27
        +4

        Nawww.

        Anyway… I cant find the info for Vic, but I can find it for NSW. I would imagine being that most of these are based on an Australian Standard, and most states use the SCAT system, it would be similar in Vic.

        Scroll down to section 4.5 (page 23) and it goes into what the "All Red" timer function is set up to work as.

  • Porker on 10/08/2022 - 14:28
    +3

    It depends on the road and volumes.

    Typically, signals on main roads will include the SCATS (Sydney Coordinated Adaptive Traffic System) which will alter the amount of green time depending on time of day and may also do it based on congestion levels. Victoria uses SCATS

    The system will also assist with coordination across a number of traffic signals, for example, there may be times where you just catch the amber on one light and then the amber on the next set of lights etc, based on speed zone.

    The amount of amber (and red) time, intergreen, is generally to let traffic clear the intersection before the next leg enters. So some approaches may have less time as the distance to travel for them is a lot less (eg. a side road entering onto a main road).

    It could also be due to efficiency - eg. All-red, where no traffic is moving, can result in longer queues, so the quicker traffic is moving, the less queuing occurs.

  • John Kimble on 10/08/2022 - 14:48
    +1

    This from QLD

    https://www.tmr.qld.gov.au/Travel-and-transport/Road-and-tra…

    All-red time
    The all-red time is the time between the end of the yellow signal on one phase and the commencement of the green signal on the next phase. All-red time is used to provide a safe clearance for vehicles that cross the stop line towards the end of the yellow signal as they may be in danger of colliding with vehicles or pedestrians starting in the following phase.

    The all-red time is based upon the physical size of the intersections and speed limit of the road. Similar to the length of the yellow signal, the all-red time does not change throughout the day.

    • askbargain on 10/08/2022 - 15:33
      -1

      The all-red time is for people to complete their hook turns or honk at people who don’t complete their hook turns.

      • [Deactivated] on 10/08/2022 - 15:41

        There’s no hook turns in QLD.

        • askbargain on 10/08/2022 - 16:30

          Good thing OP isn't from QLD.

  • John Kimble on 10/08/2022 - 15:51
    +3

    Slightly related story. I was pretty lucky a few years back.

    I was at the below intersection, when the light was red. After what seemed an eternity (2 or 3 minutes?) it still didn't change to green.

    I said to my wife, what's going on, everything is red, no one is able to go, something must be broken!

    I was moments from just "running" the red (slowly), when a couple of police motorbikes came into the middle of the intersection and parked themselves there. About a minute later a few official looking black sedans drove through, in the back of one was Prince William and Kate! I think they must have just left Kirribilli House or something.

    A few more police motorbikes followed up, the first motorbikes then followed, and the light finally turned green. Probably took 5 to 10 minutes all up…

    I thought controlling traffic lights (I assume) remotely like that was only in the movies, I was proven wrong.

    High St
    https://maps.app.goo.gl/MtbdJnAMKMQyEvP47

    • GordonD on 10/08/2022 - 17:17
      +2

      Yes, traffic lights in the big cities are under central control. That control can me taken over from a helicopter. And in a lot of countries transmitters are fitted to emergency vehicles, specifically fire trucks, to interrupt the normal cycling and give them a green at every intersection as they approach. It was possible to find out what the signal those transmitters sent, and make or get pirate transmitters. These days the central control looks after that, and you couldn't get away with using a pirate transmitters for long because of the amount of video surveillance.

      • skid on 11/08/2022 - 08:21

        Yep had this happen on roads in the suburbs 40km from Sydney. Traffic lights were remotely controlled for bikies riding to the funeral of their leader.

      • Misplaced on 11/08/2022 - 10:33

        I once went through an orange light at a T-intersection. It was fully orange the entire time I was (safely) travelling through the intersection. There was an Ambulance waiting at the traffic light but it had no lights or siren going. A Police Car who had been just behind the Ambulance pulled me over. He insisted that I went through a "clean red light" although the other 2 passengers in the car confirmed that the light was orange the entire way through (and both later provided statements to that effect). The Policeman told me I was wrong and said that I "had to be colourblind". From his perspective, the light must have changed to green much quicker than usual - hence him insisting that what I was looking at must have been a red light (I can only assume the Ambulance has some sort of remote control to make the lights change quicker). At NO stage did the light I was looking at turn red. I told him that he was absolutely incorrect and that I would dispute it. Long story short, the case got thrown out.

  • grasstown on 10/08/2022 - 16:33

    Wow had no idea.

  • Caerdyddblue on 11/08/2022 - 11:29

    Thanks for all the replies, what a great site this really is!

    By "All red" I assume this includes amber? The amount of time of all lights being red is nowhere near 3-4+ seconds, more like 1-1.5.

  • wako on 11/08/2022 - 11:43

    In SA I swear the ones with red light cameras change faster than every other one they almost skip amber it seems…

    Revenue raising at it's finest

  • Peck on 11/08/2022 - 16:15

    Reverse topic. I think that I vaguely recall, I think in S.A. in the 50's, lights used to go from red to amber to green. (Get ready, Get set, GO!)
    Does anyone recall this anywhere?

  • theo96 on 11/08/2022 - 16:22
    +1

    In the UK the light would turn amber for a moment before turning to green (from red) — I found this very helpful as heads-up that the light is turning and to get ready to move.

    More places should copy this.

  • timmypete on 11/08/2022 - 20:33
    +1

    I can't recall if it covers red intervals or not, but there's a surprising level of detail released on Vicroads-administered intersections. Links in this prior comment.

    • Caerdyddblue on 12/08/2022 - 14:41
      +1

      Thanks for that link! Agreed has a lot of details but struggling to find what the exact timeframes are

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