MANALOG: TRAFFIC LIGHTS
-Mitch Hedberg
Ever sat at a light all alone waiting for it to turn? Sometimes it can take an awfully long time, sometimes you just give up waiting and drive through if it is late at night and deserted. Emergency vehicles have a strobe on top which is detected by a sensor mounted on lights, triggering a change so that they can move through swiftly to their destination. Guys like us have to sit and wait, and sometimes that wait can be a long time.
Part of the reason that wait can be so long is because of how some traffic lights work. Some are on a set timer, but others have a trigger to let them know someone is waiting at the light and needs a green to pass through.
Traffic signals started in London of 1868, amid gaslights and hansom carriages. The first signal was a mechanical semaphore at the intersection of George and Bridge streets. According to Brinkster:
These earlier lights were controlled by traffic cops, but the first automatic light was installed in Wolverhampton, England using a clockwork timer. In time these devices became more sophisticated, and by 1960 the systems included a system in the pavement which detected cars. These systems do not rely on weight, they are instead a weak electromagnet called an "inductive loop" which is a set of wire in the pavement covered with tar or rubber. When anything sufficiently massive made of iron is over the loop, it sends a signal to the traffic controller that a car is waiting, letting the light know it needs to change.
The problem is that over time advances in metallurgy and plastics means that the hulking iron cars of the 1960s have given way to smaller, sleeker cars made of aluminum, carbon fiber, and composites which means the iron content of cars waiting at a light is lower and lower. Because the EM field is so weak, smaller vehicles sometimes will not trigger the system. Motorcycles, for example, are small enough and contain little enough iron that they often simply are not noticed. Four Wheel drive trucks are so high off the ground that they won't trigger the system either in many cases. And no, your bicycle won't get noticed either.
So there's a few products out there which will help you get noticed. One such is called the Green Light Trigger, a device which you install on the undercarriage of your car. It sends out a magnetic signal that the inductive loop will recognize, even if you're riding something as small as a bicycle (because it is a powerful magnet, you'll want to be careful where you mount the thing on smaller vehicles). Other similar devices are the Red Light Changer and the Signal Sorcerer (although that company appears to have gone out of business).
Incidentally, there are devices you can get which mimic the strobe traffic light changer that emergency vehicles use, but they are all illegal. They work, but they'll get you fined or thrown in jail, and sometimes hit by cars unready for the traffic light shift.
But if you ride a bike, I recommend one of these, just to make sure you get through those lights waiting for someone to show up, because chances are it will never notice you.
Previous Man Catalog posts:
Part of the reason that wait can be so long is because of how some traffic lights work. Some are on a set timer, but others have a trigger to let them know someone is waiting at the light and needs a green to pass through.
Traffic signals started in London of 1868, amid gaslights and hansom carriages. The first signal was a mechanical semaphore at the intersection of George and Bridge streets. According to Brinkster:
Designed by railroad signal engineer JP Knight, it had two semaphore arms which, when extended horizontally, meant "stop"; and when drooped at a 45-degree angle, meant "caution." At night, red and green gas lights accompanied the "stop" and "caution" positions,The first genuine traffic light had to wait until the new century, and who first had such a device is a matter of some contention. The first functioning traffic light appears to have been in Salt Lake City, set up in 1912. The next year, one was set up in Detroit, and within a year the city had over a dozen. Based on railroad lights, these were the first lights with the familiar red, amber, and green colors for stop, caution, and go. It was Garret Morgan, said to be the first black man to own a car in Cleveland Ohio, whose perfection of the traffic light led to its patent and purchase by General Electric, setting the standard for all future traffic signals.
These earlier lights were controlled by traffic cops, but the first automatic light was installed in Wolverhampton, England using a clockwork timer. In time these devices became more sophisticated, and by 1960 the systems included a system in the pavement which detected cars. These systems do not rely on weight, they are instead a weak electromagnet called an "inductive loop" which is a set of wire in the pavement covered with tar or rubber. When anything sufficiently massive made of iron is over the loop, it sends a signal to the traffic controller that a car is waiting, letting the light know it needs to change.
The problem is that over time advances in metallurgy and plastics means that the hulking iron cars of the 1960s have given way to smaller, sleeker cars made of aluminum, carbon fiber, and composites which means the iron content of cars waiting at a light is lower and lower. Because the EM field is so weak, smaller vehicles sometimes will not trigger the system. Motorcycles, for example, are small enough and contain little enough iron that they often simply are not noticed. Four Wheel drive trucks are so high off the ground that they won't trigger the system either in many cases. And no, your bicycle won't get noticed either.
So there's a few products out there which will help you get noticed. One such is called the Green Light Trigger, a device which you install on the undercarriage of your car. It sends out a magnetic signal that the inductive loop will recognize, even if you're riding something as small as a bicycle (because it is a powerful magnet, you'll want to be careful where you mount the thing on smaller vehicles). Other similar devices are the Red Light Changer and the Signal Sorcerer (although that company appears to have gone out of business).
Incidentally, there are devices you can get which mimic the strobe traffic light changer that emergency vehicles use, but they are all illegal. They work, but they'll get you fined or thrown in jail, and sometimes hit by cars unready for the traffic light shift.
But if you ride a bike, I recommend one of these, just to make sure you get through those lights waiting for someone to show up, because chances are it will never notice you.
Previous Man Catalog posts:
posted by Christopher Taylor at 8:33 AM
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