Traffic Lights
Thursday, May 29, 2008 at 09:06amAfter sitting at a local traffic light last night, the geekboy and I got into a discussion about timers and do lights really know if your car is there or is it just dumb luck sometimes that you’ll roll up to the line and it will change and blah blah blah? I maintained that everyone talks about these fancy detectors in the road, but nobody really knows exactly how they work or if they even exist. And if there are detectors, why have I sometimes spent what felt like HOURS sitting a light in the middle of nowhere? The geekboy’s argument was basically, “Whatever, freak, it’s tiresome to argue with your know-it-all ass, look it up and you’ll see.” So I did. Turns out sensors do exist, but not every single traffic light has them. So there you go.
charlotte on Thursday, May 29, 2008 at 9:12 am
Thanks. I always wanted to know this.. Tell me hot to MAKE someone install one of these at my Shoprite. I waste valuable minutes of my life waiting for that one to change.
chuck on Thursday, May 29, 2008 at 9:15 am
I bet he loves your new gig, you know-it-all.
GeekBoy on Thursday, May 29, 2008 at 9:18 am
While it’s good to know that I was sorta kinda possibly right, I guess this still doesn’t tell us whether there actually IS a sensor at the light in question. They should have to mark them specially somehow, so we all know. Because I’m guessing I’m not the only idiot who, when faced with a persistent red light on a back road in the middle of nowhere, has rolled the car back and forth a few times trying to “trigger” the light to turn green. You know, in case the sensor was asleep the first time I rolled over it.
Chips O'Toole on Thursday, May 29, 2008 at 9:39 am
I used to do some flagging for the city crew in my howntown that installed these sensors. They do exist. They are basically a loop of metal that read a magnetic current (or create one, or something) when a big chunk of metal is above or around it. That’s why motorcycles usually have to wait, as they don’t trip it. To see if they are there, look at the asphalt. if there is a cutout in the shape of a rectangle, covered by black goo, it’s there. otherwise, nada.
I have recently read that although many NYC traffic lights have “push for walk sign” buttons, only 25% of them actually work. And Otis elevator said in the New Yorker a few weeks ago that the close door button on their elevators is basically not connected to anything, andhasn’t been for years. (I know that Kone elevators are, however)
Hugh on Thursday, May 29, 2008 at 12:20 pm
…yet I can NOT resist pushing those stupid “Push for walk” buttons.
GeekBoy on Thursday, May 29, 2008 at 12:22 pm
I know, right?
anna kathryn on Thursday, May 29, 2008 at 1:30 pm
There is a push for walk button near my house in Boston that I KNOW does not work. I have literally never seen the walk signal come as a result of pushing that button. It just appears every so often. So you basically just have to dodge traffic.
Then there’s one that does actually work and I can’t resist pushing it several times in a row to make sure it gets the message.
Janet on Thursday, May 29, 2008 at 2:14 pm
You need a sensor for the sensors!
Larrygrrl on Thursday, May 29, 2008 at 4:20 pm
We have a new traffic light here in Bloomsbury, and it has sensor cameras mounted to the overhead arm that holds the traffic light. I hope it’s just a sensor and not a real camera, because I’ve had to make last minute wardrobe adjustments in the car while waiting for that light to turn!
Now that I think of it…it’s the ONLY traffic light in Bloomsbury.
GeekBoy on Thursday, May 29, 2008 at 4:42 pm
Larrygrrl, I hate to tell you, but I’m pretty sure those are cameras — but they’re designed to record people who run red lights, not people who make wardrobe changes.
Chips O'Toole on Thursday, May 29, 2008 at 9:08 pm
Red light cameras are positioned a ways back from the lights at th e intersections. there are lots here.
That little camera type thingy on top of the lights is a strobe receptor. When emergency vehicles run with their lights on, they also have a strobe, which phases the lights in the direction of travel, so they have to cross fewer busy intersections against red lights.
Once, I was at a light, and in the northbound lane was an ambulance, lights off, but strobe on, waiting for the left turn signal, which never happened, because the light was convinced that the ambulance was trying to get through. we all waited there for minutes before the knob figured it out and turned it off.
incidentally, it’s illegal, but some people have been know to buy strobes to put in the front of their cars in order to get lights to change to a more favorable phase.
I know way too much about traffic engineering, I think.
freakgirl on Thursday, May 29, 2008 at 9:17 pm
Interesting stuff - I had no idea about any of this!
Fizanic on Monday, June 02, 2008 at 7:11 am
You can tell when the sensors are in the road because there’s a rectangle cutout near the light that is the sensor. It’s usually a pressure sensor so when your car rolls on top it will activate. You can usually notice the tar around the edge of the sensor’s rectangle cutout. The cool thing is if you roll over the edge with your bike you can alert the light that you’re there and not have to wait for a car. At least, I think I’m triggering the light.
Also, from what I understand the “push to walk” button at intersections isn’t designed to trigger the light any sooner but add time to the next cycle to allow pedestrians to cross.