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Tag Archive: traffic lights and bicycles

The story behind Veloloop

Sometimes, as bike commuters, we meet the most interesting people at stoplights. Maybe it’s because we’re not ensconced in metal-and-glass shells, so we seem more accessible. I’ve met my share of folks at stoplights; just ask my friend Gordon R, who sometimes posts here as “The Other GR”. We met at a stoplight in Tampa and became fast friends.

A few weeks ago, I was out riding at an unusual hour (for me), trying to get some night shots of a dynamo light I am testing. At a stoplight, another cyclist rolled up behind me and asked me about the light. We got to talking, and he mentioned that he is the inventor of the technology behind Veloloop.

Have you seen this thing? Veloloop uses radio signals to communicate with the induction loops that control stoplights, and triggers them in a way that bicycles sometimes cannot on their own. Turns out the inventor lives a block away from me, and holds a variety of patents. He wishes to remain anonymous for the time being, but was gracious enough to answer a few questions for Bikecommuters.com. Veloloop has already received favorable press in a number of news outlets, including Outside Magazine and Bike Radar.

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A couple of weekends ago, my neighbor and I met and he demonstrated how Veloloop works. I hung back to watch so as not to inadvertently trigger any stoplights. I can say that the device really works — my friend would roll over the induction loop, the light on the Veloloop device would blink for a bit and then go steady, and the crosswalk countdown timer would start ticking away. Seconds later, we had a green light to proceed!

BC: How did you come up with the idea?

Many years ago a co-worker asked if it would be possible to do something like this. There are other approaches in the patent literature, but I found them to all be a little less than elegant. I’ve done a fair amount of radio design, and I had studied how to make radios that transmitted while they received, and eventually I realized how to apply that knowledge to this problem.

How long have you been working on Veloloop?

I spent a significant amount of time over the 1999-2008 timeframe learning how traffic sensors work and exploring various ways to electronically activate them. Then about two years ago Nat Collins approached me because he wanted to do something similar and had seen my patents. So, we cooperated and developed a practical version.

How does Veloloop work?

First, you have to understand how the loop sensors work. They are really just big metal detectors. They transmit a high frequency signal into a loop of wire beneath the road surface. That loop has an electrical property called “inductance”. Inductance is a measure of how much magnetic field is creted by a current. When a car drives over the loop, the inductance changes. It actually goes down. This is because the metal in the car intercepts some of that magnetic field. The sensor detects this sudden change in inductance.

There are several ways to do this, but usually the sensor’s own frequency depends on the inductance, so it can notice a sudden change in frequency to indicate vehicle presence. The key thing here is that it’s a high frequency signal, and the inductance changes when a vehicle is present.

The Veloloop has a transmitter. Once it figures out what frequency the loop is using, it sends back a signal at *almost* the same frequency. In fact, the signal it sends back deliberately varies its frequency, a little high, then a
little low, etc., just to be sure all bases are covered. It is able to keep listening while it transmits to make sure it is still over a sensor and near the right frequency. This transmitted signal gets picked up by the loop in the ground and looks to the detector like a sudden change in inductance. Voila, the bicycle gets detected.

How prevalent are inductive loop traffic sensors in the U.S.? Are there other technologies to detect cars and bicycles at intersections?

They appear to be going away in some areas, and are being replaced by vision systems. Vision systems are often unable to detect bicycles and have trouble with accumulation of dirt. Inductive sensors are still common in many places and there are several well-established companies making them and coming out with new models. I expect them to be around for a long time.

What is some of the backlash you’ve seen regarding press coverage of the Veloloop in news sources? Any persistent myths that bicyclists repeat?

Much of the backlash comes from the fact that often proper placement of the bicycle over the sensitive part of the sensor is adequate to generate detections. So, there is a perceived lack of need for an active device. There is also the stupid idea that if you don’t get detected, it may be permissible to run the light.

In reality, there are many detectors that are just unable to detect bicycles regardless of placement, and many situations where it would just be a whole lot safer, faster, and more convenient to get detected. This is where the Veloloop can help. It also takes a burden off of traffic departments who often have trouble fiddling with sensitivity.

Oh, and then there’s the “magnet myth”. This is the urban legend that says that putting magnets on your shoes will somehow trigger the sensors (Editor’s note: I was guilty of believing in this myth — had a hard-drive magnet glued to the bottom of my cycling shoes back in Florida). As I pointed out, the sensors use a high frequency signal while a magnet produces a static field. They are not the same. This old idea is based on a fundamental misunderstanding of electromagnetics and has been disproven many times. What probably happens is that someone glues a magnet to their shoe or frame, and then proceeds to place their bike over the sensitive part of a cooperative loop, and gets a detection. They think it was due to the magnet, but in reality it was the placement (or the car that came by in the opposite direction). Enough people have done the scientific test with just a magnet without a bicycle at a deserted intersection, to debunk this one.

Anything else we should know? Any improvements in the works, or other details to share?

We’ve looked at eliminating the loop and using the bicycle frame as an antenna. That would involve some big up-front costs to make a special transformer, so we didn’t start there. We are also looking into the motorcycle market. We’ve have a lot of inquiries there. Neither of us (the Veloloop developers) are motorcycle owners, so we don’t have first-hand knowledge of the requirements.

Recently, the VP of engineering at a major induction loop manufacturer contacted us to test one of the Veloloop devices. He can tell us just what effect the unit is having on their sensors (trigger, error condition, etc.).

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Editor’s note: The Veloloop’s Kickstarter campaign is struggling a bit — so there’s still time to contribute if you’re interested. We’d like to thank the developer for taking time to demonstrate the device and for answering our questions. We’ll have a followup once the induction loop manufacturer submits his report, too.