Did You Know about Traffic Light Sensor (Aka Induction Loop)

So this morning I stopped behind a car which stopped short of the right turn sensor (for some reason).

At first I didn't notice but after the first cycle of light and the right turn arrow didn't turn green, I noticed he's stopping short of the sensor.

Didn't want to be an a**hole to honk him, I opened the door and ran up to him and asked if he could move the car forward to trigger the sensor. To which he said I'm full of sh*t and the light is broken. Too early for drama so I just sighed and walked back to my car hoping he would look and realise there was a induction loop on the road. Another light cycle gone and still no green arrow, he changed lane and went straight instead.

I moved my car forward and the light worked just fine.

So did you know about these traffic light sensor? and what would you have done if this was to happen to you?

obligatory paint drawing

Poll Options

  • 816
    Yes
  • 26
    No

Comments

  • +116 votes

    +1 for the paint drawing!

  • +104 votes

    Would have honked. Sensors are common. If someone doesn't know they exist, a brief verbal exchange near the intersection isn't going to undo decades of ignorance.

  • +3 votes

    Buses can get caught out on it if they're a bit far ahead and there's a car right behind it. I watched it not able to move for 10-15 minutes until a car came at opposite.

    •  

      Same today. I was hoping the opposite side would trigger the green arrow on our side, but it didn't. The opposite side turn right just fine when I stopped there and watched in despair. Haha

      • +1 vote

        I've seen this happen to bikes.
        They usually slowly backup, and let a car go in front to trigger the sensor.

        And if theres no cars, and a cop watching from across the street, then they're screwed Lol

        •  

          I typically trigger the sensor on the bike without issues.

          However, if there's a car behind me and no pedos, I'll move forward and let the car behind me naturally take place over the sensors. :)

          (awaiting pedo joke)

        • +1 vote

          There are some lights that I haven't been able to trigger with my bike. I've had to move forward and wave the car behind me to pull up close so they trigger the sensor.

          •  

            @macrocephalic: Same here. I turn around to the car behind me and gesture for them to come forward, then point to the ground. Never had issues.
            If there's no one around, I roll the bike back and forth over the sensor. Eventually, it registers.

    • +2 votes

      😂 10 minutes? I would just run the red.

      Edit: carefully

  • +7 votes

    I was once behind a motorised cyclist at an intersection like this. He wanted to turn right but his vehicle wasn't heavy enough to set off the sensor or he was in the wrong spot. Eventually he realised why he didn't get a turn sequence and rolled forward so that I could move forward and set off the sensor.

    It would be good if there were signs indicating which intersections had these sensors and instructions about where to stop the car in order to set them off.

    On a separate note, there is an intersection near me which has a sign to say that the right turn arrow will only work every second sequence at certain times during the day. I think this is to increase the straight ahead flow of traffic during the morning peak. So, not all turning lights work for every sequence.

    • +15 votes

      Just about all intersections have them and they are not set off by weight but by a change in induction. Even a carefully bicycle can set them off.

      • +8 votes

        As a “motorised cyclist”, I have had plenty of occasions that I have pulled up to turning lanes at lights and my motorcycle just doesn’t have enough metal in it to set off the loop pick up. I have often had to get off the bike, run to the pedestrian button and press it, or move forward enough to let the car behind me move over the loop.

        While some do work, it’s about a 60:40 working rate while on the motorbike. I have never had one work while using a “pedal cycle”.

    • +6 votes

      Do we really need more signs in this world of visual pollution?

    • +7 votes

      It would be good if there were signs indicating which intersections had these sensors and instructions about where to stop the car in order to set them off.

      If there's a traffic light and it looks like someone's got a box cutter and drawn a square.. then filled it up with bitumen (black rubber command), there's an induction loop

      On a separate note, there is an intersection near me which has a sign to say that the right turn arrow will only work every second sequence at certain times during the day. I think this is to increase the straight ahead flow of traffic during the morning peak. So, not all turning lights work for every sequence.

      Yeah, looks like some traffic lights are controlled by timing or on-demand during night time which is good.

      •  

        If there's a traffic light and it looks like someone's got a box cutter and drawn a square.. then filled it up with bitumen (black rubber command), there's an induction loop

        What about on roads that don't have traffic lights, what do those do then?

        • +2 votes

          If you're referring to freeways, traffic management and live estimated travel time. Ramp signal timings are adjusted based on traffic volume detected on the freeway.

          •  

            @ascorbic: Yeah, notice those from cwongtech's description on the freeway…could be on other roads too and not just the freeway, I remember there was on some high ways….. Definitely one on Reid Hwy somewhere.

            What do you mean by ramp signal timings? What ramp?

            traffic management and live estimated travel time

            Is this where google gets it's live traffic estimation of travel time from point a to point b in google maps?

        • +2 votes

          Normally there are two separated by less than 10 meters. Used to calculate flow rates and car speeds.

    • +1 vote

      his vehicle wasn't heavy enough to set off the sensor

      The cyclist must have been in the wrong spot because induction works on EMF.

    • +2 votes

      Look for a large rectangle in the lane just before the stop line & yeah, they are triggered by metal. I was painting in a shopping centre car park & could trigger them with a 20 litre metal paint tin.

    • -2 votes

      Every intersection has these loops.

      You need a certain amount of metal on your bike and you have to position the metal part of your bike over the actual loop itself ( not in the middle or outside )

  • +6 votes

    As a cyclist, you gotta know where the induction loops are. Otherwise you aren't going anywhere.

    •  

      I heard that bikes usually don't have enough metal to trigger it so some cycles attach strong magnets on their bike to assist with this.

      • +1 vote

        The gates at my work have one, I find if I stop by bike on and move back and forth a few times it triggers

      •  

        Yep. The bane of my life while out on the motorcycle is turning lanes at lights. Sometimes it’s ok, other times it is pointless and you just have to wait for a car to pull up.

        I have more success with them if I pull up over the length of the lines rather than across the middle. Still hit and miss though.

        •  

          Same. The car behind me is wondering why I am frantically gesturing at them to move their car up. Heard plenty of solutions, carry a neodymium magnet around, etc, couldnt be bothered trying them though.

          • +1 vote

            @cannedhams:

            Heard plenty of solutions, carry a neodymium magnet around, etc, couldnt be bothered trying them though.

            This one is fake.
            I've tried it.

            You can't trip a sensor with a RE magnet, but you can with a shopping trolley or A4 piece of aluminum foil (the larger the better)

          •  

            @cannedhams: My solution is actively avoiding roads which have them, or you can try running to the nearest pedestrian crossing and pressing the button to activate that light.

        • +1 vote

          Put a rare earth magnet in your sole or wherever possible, works for me :)

          • +1 vote

            @apptrack: Doesn't work.

            The same induction loop system is used in automated garages (going outside), when a "car" goes ontop of the induction loop, it will trigger the garage door to open.

            It's the same thing for an older shopping centre carpark (that doesn't have carplate recognition yet).

            That's why if you ever try to walk up to press a ticket, it will go "Please drive vehicle up to gate!".

            P.s. a shopping trolley is a vehicle ;) ;)

    • +25 votes

      Lol cyclists don't stop at traffic lights

  • +5 votes

    Was stuck behind a Unimog once (way too "tall" for the induction loop even though he was right on top of it). 4 sets of lights he sat there…

    I probably could have just driven under him!

  • +12 votes

    Best drawing ever
    You should submit it to the local art gallery

  • +1 vote

    Illegal and unsafe to get out of your car, actually. :p

  • +34 votes

    People who sit so far back from the stop line or from other cars cars in front are a real pet hate for me.

    They don't realise that by leaving huge gaps they are making the line longer than it needs to be, and often also blocking other people who want to use a turn lane that comes off the main lane they're blocking.

    • +2 votes

      I've had people taught to drive in other states tell me that they were taught to stop so they could just see the rear wheels of the vehicle in front. I could understand that when they first started driving, but couldn't quite understand how they passed a test like that.

    • +1 vote

      I’ve always wanted to say this but could never word it better than you did

    • +2 votes

      I understand it makes a difference for turn lane, but for normal lanes it doesn’t matter. What matters more is to keep safe distance and constant speed without unnecessary acceleration, breaking and changing lanes

      • +1 vote

        They are talking about a stopped / stationary state.

        And it can matter for other lanes too, for example keeping large gaps waiting at a rail crossing that runs back to traffic lights means other traffic cannot move forward.

        It's all really just about mindless inconciderate drivers on our roads.. Only thinking about themselves, this is where most of the problems come from

    • +1 vote

      Agreed on the turn lane. However there was a study that showed there was less congestion and faster moving traffic if people left larger gaps in front of them at both:

      1. The light
      2. When driving

      Interestingly point 1 only applied if people were paying attention to the light or the car 2 in front. It meant that almost everyone could start accelerating at the same time when the light turned green, without fear of rear-ending.

  •  

    Should have honked. What age and nationality did he look like?

    •  

      What age and nationality did he look like?

      What does it matter?

      • +6 votes

        I'm wondering if it's a generational thing or being from a different country for not knowing.

        • +2 votes

          I learnt to drive in the UK and was driving here for 5 years before I knew about induction loops. It's not a thing over there, they don't have right turn filters (you just sit and wait for ages for a gap in the traffic)

          •  

            @dp1: "It's not a thing over there,"

            They might have replaced them all, though I doubt it.

          • +2 votes

            @dp1: I remember my dad telling me what the induction loops do at lights in the UK, and that was in the early eighties (long before I could drive!)

            Also by the late eighties some cities in the UK had fully-managed light systems, so that you could drive through the city at night (or any time with little traffic), and the lights would go green ahead of you getting to their triggers (as long as you kept going straight through).

            Alan.

      • +1 vote

        It does actually, an example is VicRoads allows tourists/people with overseas driving license to drive in Victoria without having to learn anything about local road rules. I always hate it when some people don’t know who has the right of way in intersection.

    •  

      I mean seriously.

      I’m creating the OzBargain Law: ‘As an online discussion on any topic on OzBargain grows longer, the probability of the introduction of race or nationality approaches 1’

    •  

      I really prefer not to say. But he's not Asian :-S

  • +10 votes

    I see a lot of uneducated drivers do this..
    Maybe they should incorporate this into the driving knowledge test so people know how things work.
    Education is key!

  • +2 votes

    google SCATS

  • +1 vote

    Sometimes if you press the correct pedestrian button it will trigger the corresponding light for vehicles.

    •  

      Yep, I have to hop off the bike, run to the button and run back sometimes.

      •  

        People keep talking about hitting pedestrian buttons but I don't see how it's related to the OP, it can't be applied in this right hand turn scenario…

        Straight, yes.

  •  

    Looking at your drawing he was parked close enough to trigger the sensor..

  • +5 votes

    PET BEEF

    In a specific turning lane, mainly right turns, where the lane is specifically cut out for that purpose, the sensor should be at the START of the lanes as well as just behind the stop lines.

    Point being, if you know the lights are about to go green with a red arrow (unless a vehicle has activated the sensor, in which case the green arrow will show), you have to get to the sensor in time so as to not have to wait a full cycle for a green arrow.

    So… in that case, if you bottle it down the turn lane you MIGHT hit the sensor in time, but if you don't… another frustrating incident waiting a full cycle for what might have been a millisecond too late for the sensor to know there is a vehicle there for the green arrow change.

    Now… if the sensor was at the start of the turning lane…

    Yes, I had a job as a time efficiency required driver.

    • +1 vote

      I can understand your frustration but overall traffic flow around the intersection would be less efficient if that's where the sensor was located.

    • +2 votes

      Also when people are too slow to take off when the light is green, the sensor uses the time between cars to estimate the number of cars waiting and when the time is greater than it should be for a line of cars, starts to switch the turning arrow off.

      When the first few drivers are distracted it can cause a shortened sequence and make others have to wait.

  • +4 votes

    Yes, fun fact - most of the time they don't detect motorcycles.

  • +1 vote

    Aside from the other comments, the other driver sounds like an ass-hat and a half. Apart from traffic lights flashing orange, in my experience it would logically be very rare for traffic lights to be "broken". Usually it's easy enough to tell where the induction loops sit with all the more reflective/shiny tar covering up the cuts in the road.

    +1 for the diagram. The RMS should update their learner's handbook illustrations with yours :P

  •  

    Some locations have the sensor 20+ metres from the lights for trucks, so they don't have to come to a complete stop.

  • -1 vote

    At one of the intersections I go through every work day the sensor is at the second car spot. So if no car is following me into the right turning lane, I stop at the second spot to trigger the green arrow.

    •  

      I thought passing over it would be fine…

    •  

      I do the same regularly, this set up is common where the light will operate regularly (every second or third cycle) even if no car is waiting, but will operate every time there is more than one car waiting. Passing over it may not trigger it as it is only checked to be operated at certain points in the cycle so I will stop over the sensor until either the light changes or another car comes up behind me.

      Red turning arrows are my least favorite traffic signal as I have spent way too much time waiting while it would be completely safe to turn.

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