Abandon All Hope…

…ye who enter here:

Sensor Loop

After a recent weekend where I couldn’t trigger a traffic signal for the life of me, I sat down to do a bit of research. A quick search for – traffic signals not triggered bicycle – yielded ~465,000 results. As part of this search, I found a blog by Nome Agusta detailing his court battle regarding these pesky detectors. When you have a few moments check out Post 1 and Post 2. I decided to see how tolerant my local constabulary would be in the event I ultimately gave up the wait and ran the red light. What follows is the e-mail exchange between myself, the administrative officer who first replied and a city traffic engineer that he went to for clarification. Okay, I’ll admit that deep down I was hoping they’d be a little less helpful and a little less polite; they were quick to respond and are trying to see what they can do to help. I’ve left the names of the people and streets out of this post. See what you think.

Me: I commute by bike and the majority of the traffic signals I encounter during my trip aren’t triggered by a bicycle. In that situation, is it appropriate to run the red light?

Officer: Bike riders are required to obey all traffic laws. I see your problem but I must tell you what the ordinances state. You could trip the pedestrian push button. See if that helps.

Me: Yes, it is a Catch 22. I have been doing exactly what you suggest with the pedestrian push buttons (when they are available) however that entails my having to, sometimes, jaywalk in order to get to the button. Example: Southbound [Street A] at [busy, Street B] has a left turn lane and a right turn lane — I need to turn left so am quite often left standing in the middle of three lanes (one northbound). I have to make sure no one headed west on [Street B] is going to be turning right, no one headed east on [Street B] is going to be turning left and no one headed south on [Street A] is going to be in the right hand lane so I can put the kickstand down on my bike, leave it in the center lane, jaywalk over to hit the button which, most days, immediately turns the light on [Street B] yellow and jaywalk back to my bike hoping to make it into the intersection before my signal turns yellow.

I heartily agree that bike riders must obey all traffic laws, but the design of many of our intersections prevent a cyclist’s ability to obey one law without breaking another. Can the sensitivity of the sensors be adjusted to accommodate bicycles? – and if so, who would I contact to give them a list of intersections to check out?

Sorry if this is a bit of a rant – but I want to do the right thing – and – remain safe while I’m out on the streets.

Officer: Let me ask the traffic engineers about the sensitivity issue and see what they can tell me. I will then let you know.

Two hours later I received the following:

Helpful City Traffic Engineer: Warren,

I wanted to take this opportunity to respond to your concerns regarding detection of bicycles at signalized intersections. I certainly appreciate your frustration. This is an age old problem that has plagued the traffic industry for many years. Unfortunately, there still is not a fool proof solution. We have different kinds of detection depending on the intersection. The type of detection at [Street B] and [Street A] is induction loop. This consists of a series of cable loops sawed into the actual pavement surface. We use a series of diamond loops because they are more sensitive and detect better than other forms of induction loops. However, there are still limits. Based on the technology, it will only pick up metal objects that pass through the detection zone. It is much like passing a metal rod through a coil of wire, like we used to experiment with in science class. When there is a change in the inductance field, it triggers a call to the controller. When vehicles drive over the loops, we generally never have a problem picking them up because of the mass of metal and their physical size. We do have some success picking up motorcycles, although this is not close to 100% of the time. Bicycles pose a unique challenge, especially with the graphite bikes that they are making. Even if they are the old heavy metal frames, it is almost impossible to detect them. We do have some ability to adjust the sensitivity at the control center. But when we do that, we begin to pick up vehicles in adjacent lanes. For the left turn movement, we would begin picking up vehicles in the adjacent southbound lane as well as vehicles in the northbound lane. These vehicles would be picked up and put in a call to the left turn phase even though there was not a vehicle in the left turn lane. This increases the delay unnecessarily at the intersection for every cycle.

The other type of detection we have is video detection. Unlike induction loops, there are no physical detectors in the pavement. It is based on a specific detection zone that is programmed on the screen based on the camera image. It operates by looking at the change in the pixel count on the camera image. When the pixel count changes by some defined number, a call is placed to the controller. In this type of detection, we don’t have to worry about picking up vehicles in adjacent lanes when the sensitivity is increased. The problem is that shadow images and debris can put in false calls when there are no vehicles present.

The industry recognizes these problems and is working toward ways to address the issues of bicycle detection. We do not recommend running the red light in any circumstance. What we would recommend instead is to exit the roadway at the intersections that are causing problems and access the sidewalk as a pedestrian. At that time, you can push the pedestrian button and cross the street like a pedestrian until you get to the appropriate side of the street. I know this is additional time for you and is not convenient. If you give me a list of the intersections that you currently have problems with, we will take a look at each one individually to see if we can adjust the sensitivity without causing other problems in the intersection.

My contact information is shown below.

[…and, it was.]

Since that last e-mail I have had a couple other exchanges with the HCTE and he has a crew that is checking out the intersections I’ve let him know about. In the event it doesn’t look like there is going to be a car around to help trigger the signal I need, I am exiting the road and using the crosswalk. Sure, it takes me a few extra seconds but I am always thinking that impatient drivers shouldn’t complain about the couple extra seconds my presence is costing them… In the mean time, there are other things you can try if you find yourself stuck, waiting for a light. Look for the most sensitive regions of common inductive loop patterns. You may even want to try laying you bike down across the loops.

A more detailed description of how these loops work can be found HERE.

Any other helpful hints?

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0 thoughts on “Abandon All Hope…”

  1. Fritz says:

    1. Police officers are *not* lawyers.

    2. You may “run” defective traffic lights.

    3. The police might ticket you regardless if the law. You’d have to fight the ticket in court.

    4. Local judges are often jerks, so you might not prevail in fighting the ticket even if the law is on your side.

    5. I’m not a lawyer, either. This advice is worth exactly what you pay for it.

    See what John Allen writes in his book “Street Smarts” under Tough Situations: Always stop and wait for red lights. You not only ensure your safety, but you also increase respect for cyclists as law-abiding road users.

    But some traffic lights don’t turn green until they receive a signal from a metal detector buried in the pavement. Some of these detectors do not respond to bicycles.

    You can recognize the detector by a square or octagonal pattern of thin lines in the pavement, where slots were cut for the detecting wires. The detector is most sensitive if you ride along one of the wires. (Sometimes, the slots for the wires are not visible, as the street has been repaved since they were installed).

    If your bicycle doesn’t trip the detector, you have to wait for a car to do it, or else you have to go through the red light. Going through the red isn’t against the law, because the light is defective. If you ever have a crash or get a traffic ticket because a traffic light won’t turn green, it’s the fault of whoever installed the detector.

    Detectors that work for bicycles are available at little or no additional cost. Design guidelines exist for these detectors. If you want to promote better conditions for bicycling, alert your government officials about road conditions of any type that are unsafe for bicycling. Let them know that they are responsible to make the roadways as safe as possible for all types of vehicles, and that accommodation of bicycles is important to you. Getting involved at the local level can be very effective.

  2. Richard says:

    I agree with Fritz. Most traffic codes specifically say that you are allowed to “run” a non working light. The details of how and when you can do that may be variable. In Seattle, you are required to wait a full light cycle, if you are not given your rightful turn by then, then you may proceed through the intersection. I suspect there is a caveat that you have to yield to other vehicles as well.

    That said, I’ve never had a problem tripping a light. But, I don’t ride a cabon bike. Many intersections in Seattle have a white “T” that marks where the hub of your front wheel should be. If there is no “T” then I line up the front and rear hubs over the loop. This may require skewing your bike depending on the size of the loop.

  3. Dan says:

    I give it one and a half full cycles, and then I go when it is clear. I guess I’ve reached the point in my life when I don’t really care about the ticket, and I could have some fun fighting it in court.

  4. There are these high-strength magnets designed for motorcycles that will supposedly trip the sensors reliably. I haven’t tried them, but I have heard of people who have strapped them under their bottom bracket and have good results. One example here: http://www.casporttouring.com/store/merchant.mvc?Screen=PROD&Product_Code=13000&Category_Code=Specials

    Where I live in Bellevue, Washington, the city has marked the most-sensitive spots with white painted X’s in the road so that you place your front wheel there to trigger the light. I ride a steel-framed bike and I have no problem triggering any of the lights that I encounter in Bellevue or Redmond. I don’t even have to bother with the white X’s, either–one of the nice benefits of a big steel bike.

  5. JiMCi says:

    Two out of many options:
    – On your top picture, there’s a nice pole, perfect to fit a button wired to the loop. Stop at red, push the button and get your green light.
    – Can’t remember exactly the city, I believe it’s Seattle… There have painted marks on the pavement showing cyclists exactly where to stop to trigger bike specific sensors that control traffic lights at bike lane crossings.

  6. Fritz says:

    Many bicycle friendly cities mark the spot where cyclists can best trigger the light. In my old hometown of Longmont, Colorado, all new traffic signals must be optical sensors that can detect bikes, and the city is also replacing all older loop detectors with the optical sensors.

  7. Fritz says:

    I found out that some states allow “malfunctioning” traffic signals as an “affirmative defense” for running red lights. In other words, it’s an automatic get-out-of-jail-free card if you’re ticketed while running the light. According to this website, this law is on the books in Minnesota, Wisconsin, Georgia, Tennessee, and Idaho. So it looks like the practice of considering a light defective may not be entirely legal in other states.

    I’ll still run the lights, though, if the light is defective.

  8. John says:

    In NYC, I have “run” red lights right in front of traffic officers. In fact, I do it all the time. As long as I can see that there is absolutely no traffic coming in either direction, I’ll take the light. NYC traffic cops don’t seem to mind. Of course, that’s NYC, where the city treating cycling as a low priority has made it a complete mess.

    However, I always do stop before the crosswalk, and if it is being used by any pedestrians I’ll wait.

    Sometimes logic outweighs technicality. The idea of someone letting minutes go by at a completely car-less intersection just because of a technicality is borderline absurd.

  9. Eric says:

    Here is some info I have gathered on controlling traffic signals with your bike.


    Most signals with loop or video detection can be tuned to detect bikes, and there are ways you can trip signals that are out of tune.

  10. Fritz says:

    Tuning loop detectors to detect bikes (and motorcycles) isn’t always so simple. If they’re sensitive enough to detect bicycles, many times they’re also sensitive enough detect a truck traveling in the opposite lane and other false detection scenarios.

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