Red Light Sensors 101: A Fragment

As has been mentioned and complained about countless times here at Better Burque, an eternal existential question cyclists face when riding a bicycle up to a red light is:

“Do I exist?” And more metaphysically: “Does the Red Light know I exist?”

Here’s an example. Let’s say you’re riding on Edith Blvd. approaching Mountain Rd. just west of Albuquerque High School on a lazy Sunday morning. It looks something, actually exactly, like this:

sensor edith and mountain

It’s just you on a bike, with zero drivers/cars anywhere in sight. And those god-like red lights staring at you. Unchanging. For well over a minute. You question your existence. You even question whether your compliance with certain roadway laws matters…because if you don’t exist, are you really breaking the law?

We’ll leave the deeper moral, existential, metaphysical, epistemological, and ontological questions raised by scenarios such as these (who knew transportation was so philosophical?) to the more abstractly enlightened, and instead will merely pass along a few specifics learned at last night’s meeting of “The Bicycle Committee” regarding roadway sensors.

For starters, let’s look again at the Sunday morning tableau at the intersection of Edith and Mountain:

sensor edith and mountain with pointers

See the black line pointed at by the highly professional and artistically advanced “pointers” found in Microsoft Paint, Version 1997? That black line is one of four outlines of a sensor “box,” in which an induction loop sensor is located. Here’s a better shot of almost the entire outline at Indian School and Carlisle looking westbound:

sensor box indian school and carlisle
Now that you notice these think black lines you’ll pretty much never “unsee” them. Interesting that they’ve been there all along. Note also that the bike lane doesn’t have a sensor.

If you want to know more about sensor installation, here is a You Tube video illustrating this very thing (Warning: This might be the single most boring video in You Tube history):

In short, loops of wire are installed along cuts in the pavement we eventually see as the thin black lines. These wires are hooked up to an “inductance meter” connected to the red light “brain” and pass along information concerning when something big and metal passes into the coiled area.

Why metal? Because the loop is magnetic. It detects metal objects. Hence, steel-frame bicycles are somewhat more easily detected than aluminum or carbon-framed bikes, but, fortunately, bike rims made of metal work for detection, too.

And this is where we get to the all-important aspect of sensor sensitivity. What we found out last night is that sensors can be set from 0 to 14. The single reason why bicycles/cyclists passing over/through sensors are not detected at many intersections around town is that the sensor is set too low to detect them.

Here’s what is being done about that:

    1. “Fixing” detectors to see bicycles is merely a matter of cranking the sensor up closer to the highest setting of 14.
    2. As your humble blogposter recalls, 8 is too low/12 gets the job done (or something like that).
    3. The City is now in the process of adjusting sensors to better detect cyclists/bicycles.
    4. Cyclists are encouraged to call 311 if a sensor doesn’t detect them/their bicycle.


  1. Regarding situations like Indian School at Carlisle, where a popular bike “facility” does not currently have a sensor in the bike lane, the City tells us that any future work done at such intersections will include installation of a sensor in the bike lane.
  2. Yes, that does mean the “best way” to be sensed at such intersections is currently leaving the bike lane and riding onto the driving lane coil, but only, of course, if that sensor has been turned up high enough to sense you/your bicycle.
  3. No this isn’t a great “best way,” but it’s reality at present.

Your humble blogposter is certain he is leaving out some important details, but the list above does get to the rather simple heart of a seemingly enigmatic philosophical dilemma.

Yes, bicycle riding person, YOU DO EXIST. The Red Light God does KNOW YOU EXIST. But only if we crank it past 11. Think “Spinal Tap,” as was pointed out last night. It’s strange, but Nigel Tufnel really is the Descartes-meets-Kant of our time.

2 thoughts on “Red Light Sensors 101: A Fragment

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