Yellow dots are like loopy buttons for cyclists

(It's been a month since my last post; I'm slowly recovering from a long stint volunteering at RBC Royal Bank Bluesfest where I run the bike parking. This year we had record numbers again!)

A topic I'm eager to write about is the yellow dots on the pavement at intersections. You may recall my epic on pedestrian buttons, No Ifs, Ands or Buttons (and the follow-up supplementary post). Well cyclists have a way of activating the signals too, and what better place to describe it than the brand-new traffic control signal at Bronson and Arlington:

To recap the lowdown on ped buttons: when there is a traffic control signal with buttons, and there is a little yellow sign above the button, that means you must press the button if you want the walk signal to activate (though for some such intersections there might be some times of the day or week when the signal changes on a fixed timing whether or not the button is pressed).

Even if the light turns green, the walk signal might not activate automatically because the signal goes through a timed cycle without activating the pedestrian light by default, or because a vehicle triggers the signal loop embedded into the pavement, which activates the green light, but not the walk signal (to the frustration of many pedestrians).

Here you can see the cuts in the asphalt where the signal loop was installed, connecting to the handhole under the sidewalk at the bottom of the photo (and from there to the intersection's control box). The loop works a lot like the pedestrian buttons, except it activates automatically when the metal in a vehicle disrupts the signal loops magnetic field.

Because a bicycle isn't as big as a car, it doesn't always trigger the sensor (which works by detecting metal in the sensor's magnetic field). So the traffic department puts down three yellow dots to indicate to cyclists where to find the most sensitive part of the signal loop, and thus where to stop your bike at the traffic light to activate the signal.

Since one of my Bike Parks at Bluesfest was right on the Ottawa River Pathway at Booth Street, I arranged for an informational sign to be put there to help educate cyclists about the meaning of the dots. Doesn't look like any of these four saw it.

The dots have been around for decades, but most cyclists don't know about them. Word about the dots' function spreads in the cycling community by word of mouth, and given how individualistic cycling can be, that word doesn't spread very far. As a result, cyclists often will wait in the wrong part of the intersection (either too close to the curb, past the stop line, too far into the intersection, etc.) and will get frustrated and run the red light. When I do tell a cyclist about this for the first time, they're usually surprised and even skeptical that such a useful tool could have been right under their noses all this time.

There have been calls to use a painted stencil of a bicycle as a more clear indication, like this one in the US Department of Transportation's standards, but there are operational problems with that.

The road painting section and the traffic signal section are two different groups, so in order to paint a stencil like this, a painting crew needs to meet a traffic signal crew on the ground to tell them where to paint it (or at least they need to mark it in advance). But because the yellow dots are easy enough to install (a couple workers and a blowtorch), it's much cheaper and more efficient for a traffic signals crew to just locate and install the dots themselves.

As a compromise to try to make their function more obvious to cyclists, the City has started (as of less than a month ago) to use yellow dots that have little bicycles cut out of them. The dots added just a couple days ago at Bronson and Arlington (thanks to Lana for pointing out the need) have this on the approach from the east along Arlington:

In that example, you can see the cut in the asphalt where they installed the signal loop, so if the dots aren't there or they're worn out, you can still guess where to put your bike to get the best results. But sometimes the loop is installed before the final layer of asphalt, meaning they don't have to cut into the asphalt to install it. In these situations, when the yellow dots aren't there or they've worn out, it's next to impossible to guess where to place your bike. Of course, this only applies to intersections where the traffic light isn't on a timed signal and needs to be triggered. When there's no visible loop, you can tell which ones these are, naturally, by the little signs above the pedestrian buttons. If a pedestrian needs to activate the signal, then so will you on your bike. Otherwise you just need to wait for your turn in the timed cycle.

Until they put the dots down on MacLaren at Bank very recently, I was entirely unable to get the signal to activate with my bike. I'd have to wait until a passing pedestrian pressed the button (which was not often, as most people just jaywalk) or sometimes after waiting a few minutes and adjusting where I'd put my bike, I gave up and just ran the red.

Here's a closeup of the dots on the west side of the Bronson/Arlington intersection, where the loop is beneath the top layer of asphalt unlike on the east side. It's these situations where you really depend on the dots in order to get the light to change:

Here are some other tips and tricks on traffic signal loops:

You might have experienced the frustrating situation where the light in the other direction turns yellow, then back to green (instead of turning red to let you cross on your green light). What's happening here is that your bike was on the signal long enough for the light in the other direction to start to change, but you moved forward past the stop line when the other light started to change. As a result, the signal doesn't detect you any more and it assumes you turned right on the red and are no longer waiting at the red light. Therefore, you no longer need the green light and it no longer needs to give a red to the dominant traffic in the other direction. The lesson here: always stay behind the stop line and wait on the dots until the light turns green.

As with pedestrian buttons, the results aren't always instantaneous. For example, Bronson/Arlignton is synchronized with Bronson/Catherine. Since Bronson/Catherine is on a fixed timing, the light at Bronson/Arlignton—when activated—will only start to change at a time that jives with the Bronson/Catherine light.


Traffic signal loops aren't just used to activate lights (though that's the only situation I'm aware of that uses the yellow dots). For example, they're also used to detect red light runners and activate the cameras. But also...

On arterial roads in the suburbs, there are traffic loops back a certain distance from the light to detect if someone is approaching the intersection at just the right speed where the light will turn yellow right as they get to the intersection. The split-second indecision of seeing a yellow light right as you're about to enter the intersection can be distracting and can lead to poor decisions (like braking suddenly when someone is behind you). To alleviate this anxiety, when this loop is activated, the green light gets extended by anywhere from a fraction of a second to a couple seconds to let them through on a green light.

Some intersections have a loop so far back it's nearly at the next intersection. This is to detect whether traffic is backed up all the way to the next block. If this is the case, traffic in that direction might get more green light until the situation clears, to avoid blocking up the next intersection back.


A similar situation occurs at some protected left turns, and this is one you can use to your advantage. From a traffic management standpoint, a single car waiting in a left turn lane isn't a problem, but when they start to queue up it risks backing into the through traffic lane and increasing congestion. So there is sometimes a signal loop in the left turn lane two or three carlengths back. When this signal loop detects a vehicle over it, at the start of the next signal cycle it gives a left arrow to that lane, where otherwise it might just be a 'green ball' (as a regular light is known in the biz). The upshot of this is that, if you are coming to a red light and want to make a left turn without worrying about traffic coming in the opposite direction, wait back on the signal loop and it'll give you a left turn signal. The downside is you'll have to deal with the motorists behind you who are frustrated that you are two carlengths back from the intersection, but don't realize that you're doing this to get them a green left arrow too. I use this regularly at Booth Street southbound at Wellington/SJAM, and on Parkdale northbound at Wellington West. (Some left turn lanes use different methods to decide when to give you a green arrow).

Oh, and if the yellow dots aren't working for you, call it in to 3-1-1. Sometimes the signal loop needs to be adjusted so it is more sensitive, or there might be some other defect.