Much discussion has taken place recently, on this blog, over the signs and road markings involved in allowing a stopped bicycle to turn a light from red to green. Traffic engineers and other planners stopped by to weigh in on the intricacies of properly installing inductive loop sensors, pavement markings and signs.
Since many of the commenters were from out-of-state, they were unaware of and appalled by the variety of signs we have here in Massachusetts. We are not the only state to have either few or inconsistent bicycle signs. Some states have virtually no signs instructing cyclists to wait on a line for a green light. Those tend to be the same states where bicycle laws are very weak and cycling for transportation is not encouraged or supported.
Massachusetts, primarily in the Boston area, is committed to making the roads accessible to bicycles. As much as this might annoy hurried motorists, it’s really in everyone’s best interest due to the horrendous traffic and ongoing congestion on Boston city streets.
This congestion has found its way outside of the city proper. Towns bordering Boston have bumper to bumper traffic during rush hour and during other busy times — such as when there is a special event.
Part of the problem is that many roads are old and narrow. They were never meant to carry the number of vehicles on the roads today. This is why encouraging bicycling is so important here.
Every person traveling on a road by bicycle represents one less potential motor vehicle on that road. Bicycle use creates more space on the roads for those who either must drive or who just prefer to drive.
The vast majority of commuters or utility cyclists ride some form of metal bike, either aluminum or steel. Most people see such bikes as capable of triggering the sensors in the roads to trigger the green lights.
Such an assumption is correct, but not entirely for the reasons one would imagine. A little research will tell us that it’s not really the frame that causes the bike to be detected, but rather the wheels and cranks.
The reason for this is that the loops in the ground don’t just detect metal, they have an electric current running through them. When a metal bicycle rim is positioned over the most sensitive part of the sensor, it disturbs the electromagnetic field running through the wire and triggers a green light. This is why the pavement markings which tell cyclists where to position their bikes are so important.
Set-ups like this work well for most bicycles because the average cyclist has aluminum rims. But, as a reader of my blog asked on my last post, what happens if the bike is carbon? Does this still work?
It depends on the bike. According to an interesting article on this subject, written by a columnist from bikeportland.org, if a cyclist has aluminum rims and cranks on his carbon bike then he should be able to trigger the light (sensor manufacturers will tell you), however “if you have a full carbon fiber bike, carbon fiber wheels, and carbon fiber components, you could be out of luck.”
In other words, a full carbon bike won’t have the metal necessary to disrupt the electromagnetic field. Cyclists who ride such bikes will have to resort to other methods to safely travel across an intersection.
Even though we learned from commenters on previous posts about how much work went into choosing designs for these bicycle signs and pavement markings, maybe it’s really time to invest more in newer technologies — ones that don’t rely on metal to sense someone waiting at the light.
As I was researching this, I came across several articles written in the late 1990s and early 2000s. These articles were talking about the same problem which has caused me — and countless other cyclists — great frustration in recent years, namely a bicycle’s inability to trigger a green light.
Fifteen years has gone by and other than changing the design of the signs and possibly improving the quality of the sensors, not much has changed. Back then, they spoke of emerging technologies.
In a bicycle FAQ compiled in the late 1990s and early 2000s, I found an interesting comment from a traffic engineer. Although there wasn’t an exact date on his comment, the ones around his were dated in the early 2000s. He said:
“Advancements are under way that may make traffic loops obsolete some day. In particular, radar, infrared and sound detectors have been introduced. Systems based on video cameras are especially promising. Such systems can easily detect bicycles. Such a system may even be able to detect pedestrians some day.
Bob Shanteau, PhD. PE
Registered Traffic Engineer”
A decade ago advancements were underway. Yet, the street I photographed a couple of days ago, which had just been redesigned, did not take advantage of any of the newer technologies mentioned by Bob Shanteau. It’s surprising that with video cameras at many intersections nowadays no one can integrate those cameras with a system that allows cameras to detect vehicles or pedestrians waiting at a light.
Maybe the increased use of carbon as a bicycle material will change all that. While it’s true that most people don’t ride full carbon bikes, many bikes built with carbon frames contain fewer metal parts than bikes did in the past.
If the time comes when many recreational or commuting bikes are made of carbon, we will have to begin thinking about how those bikes will use the roads. Begging and pleading for infrastructure hasn’t changed much in the way bicycles trigger lights.
Instead it could be the evolution of bicycle materials which brings about this change, through necessity. One technology can give rise to another. And technologies can affect one another.
On our own we are taking baby steps to improve bicycle infrastructure. With any luck, bike manufacturers will force our hands and will bring new technology, which suits all road users, into common use.
