*New* traffic light sensors
 

Lots of posts here about the old induction coil sensors. I recently spoke with a local traffic engineer about one of the newer traffic light sensors that are being used in newer signals. Thought it might be of general interest.

The lights use a "mass sensor"... a camera-looking thing mounted a couple of feet above the boom. (They can't be mounted on lights suspended by wires... no way to fix the detection zone.) There's typically also an emergency vehicle detector, the thing that looks like it has a floodlight, mounted on the boom. The sensors have a fairly confined detection area, typically set up for an area from 5' in front of the stop bar to 30' behind it, and is pretty narrowly focused on the lane, so activity outside that (e.g. pedestrians) don't trigger it. There is also a sensitivity adjustment, and there is a reset mechanism, so cars that roll up to the light and then turn right on red don't trigger a green. All these settings can be adjusted. The engineers advice to me was that if there were no cars, I should be sure I'm in the detection zone. I find they work the best if I roll up to the bar, and stop near the center of the lane. And if the light doesn't respond, notify the appropriate local DOT that it needs to be adjusted.

Edited for you...

Seriously, I've seen these going in around here. Of course, the intersections they are putting them in at are intersections so busy I'd never ride on them. The inability for bikes to trip sensors is why I have stopped caring about whether they get tripped or not.

some of our sensors trigger nicely with bikes, most don't. I found one that triggers if I ride up between the two sensors. Not sure how that works, I actually figured that out one time when I didn't want to trigger the light since I was running it ;)

What!?! So a pedestrian that pushes the walk button is rude and arrogant? A single motorist crossing a busy street is rude and arrogant?

:roflmao2:

genec, please see http://en.wikipedia.org/wiki/Troll_(Internet)

OP:
We have some of these new "improved" lights here in our small town (there are only 4 lights in the entire town). They stink. Half the time they don't even see my CAR. Sure, they're probably adjusted wrong, but try getting anyone to fix it. They can't even get it right for a car, I don't have much hope for bikes.

I never had any trouble getting an induction loop to trigger for my bike, except when the loop had been paved over, then I had to figure out where it was.

Uh, no problem, but chipseal usually doesn't troll. Perhaps this was his exception, or he was trying to be funny. Only he knows for sure.

I had a conversation with a couple of road engineers/installers near my house the other day. They were modifying the light controller and lights at this one intersection. The intersection has not had a left turn arrow in the past, and it appears that change is being added, along with a new controller box. (this effort BTW has taken nearly a year... )

I talked to these guys as neither one of the local intersection lights will sense my bike on a consistent basis. (I have submitted requests for adjustment many times). Turns out that the old systems are from the mid '60s and are relay driven and really offer little adjustment, and as one engineer stated, "sometimes the wires are installed too deep or are not installed properly..."

The newest system they are installing is one of those vision systems. They said it would "sense a human standing in the street" (at the right spot) and trigger the light. Of course I then mentioned... "where is the right spot?"

With the sensor loops sometimes you can see the loop and put a wheel right on it. (they mentioned the "hot spot" is right on the wire loop anywhere) But sometimes these loops are paved over and are invisible... so where is the hot spot?

That is one of the key issues... small targets, bicycles, may not be in the right location, and if there is no way to see the "right location" then it doesn't much matter how good the new systems are.

When they finally get finished installing this system I am looking forward to testing it.

Useful to know, but I usually just "look both ways before crossing the street" and then go when it is safe to do so. If there is enough traffic that you actually need the lights to change to get across, then chances are there are cars waiting with you which will trip the sensor for you anyhow.

Not always. I live in a small neighborhood bounded on two sides by arterial roads; during the busiest times of day, those roads hold a steady stream of traffic... there is no way to cross or merge without somehow slowing the flow.

The other two sides of my neighborhood are steep high walls down into canyons...

Since this is a small neighborhood "island," there isn't that much other traffic to ensure that someone may come along and trigger the light with me. Often I am on my own. Many times I am forced to simply walk the bike to the corner and act like a pedestrian and push the walk button as my only recourse.

None of the induction loop detectors here in central Arkansas will work for bikes, but I've had good luck with the camera detectors. What these things are keyed on is contrast with the pavement in the backgorund, so light-colored clothing helps; headlights help even more; especially at night. If you're in ninja mode or close to it, other travelers have a hard time seeing you, and the camera will, too.

Well that sounds like it would be annoying!

Normally, yes. On my ride home, I have a busy cross street - but the road I am on has almost no traffic (which is why I use it) Sometimes it'll trigger. Sometimes a car will come up and right turn which it senses and starts changing but when they leave it goes back to red. I have resorted to pushing the ped crossing button if the traffic is too steady, otherwise I wait for a break and cross or a car will show up.

Cool, thanks for that.

Our lights in town are all run on timers so the motorists can have a clean drive for multiple streets without having to stop at every street for a red light. In succession the light at the center point which would be the river starts green and everyone after that turns green with 2 seconds delay from the previous. This leaves just enough time to make the whole run.

It is arrogant to think that a cyclist is arrogant for taking up the street when we are certainly allowed to. I pay my taxes the same as the motorists and probably even more than most. If the DOT can not design a system that works for ALL of the people using it than it is useless and I could care less whether or not people get upset. Normally it makes no difference, because I'll just run the red light if there is nobody around. Otherwise I just wait til the light turns green.

It is.

On the flip side, during the work week the flow is only steady during rush hour drive times... other times you can easily walk across the street without even using the walk signal.

The north south arterial road is even crazier... during peak hours it sometimes comes to a complete halt. (it is then quite easy to navigate) It is marked at 45MPH, but at near peak, motorists are usually moving at about 50MPH. At other times, such as late Saturday or early Sunday, it is a ghost town. Very "schizophrenic." This is the only connecting road north and south due to the geography of the area... other than the two freeways that parallel the road. Motorists try to use this arterial as a short cut to avoid the freeway. Cyclists have no other choice.

I've found that I need to present a larger target to only one of these stoplights that I have on my route. I do an S-curve just before I get to the crosswalk so that I am sideways to the sensor. In the winter, I've found that shining my helmet light on the sensor does a great job of triggering it.

I have this one twice-daily intersection where I am, naturally, on a low-volume road, and the sensor is deviously spaced so that a car hugging the stop line and nudging into the x-walk will be in front of it, and a 2nd car that is not riding the 1st car's butt will be behind it. Anyway, I always stop right on the sensor. Often as not I am 1st in line waiting there anyway.

This is in the straight/left lane. There is a right turn lane, and there, cars pull over to the bike lane before turning right so also miss the sensor designated for them (as well as blocking bikes).

It helps me to think of the "sensed" area by imagining the sensor is a flashlight and the monitored area is in the cone of light ending in the illuminated ellipse on the pavement. (A picture would be worth a thousand words, but I'm too lazy.) It's going to be narrower at the front, so you need to be near the middle of the lane.

I work at a government facility with a security fence. There is an inductive loop embedded in the asphalt to automatically sense and open the gate for exiting vehicles. We recently hired several new employees one of whom competes in triathlons. He brought in his carbon fiber bike the other day for an after work training ride. As I was leaving the office I saw this gentlemen dragging his bike all over the loop trying to trigger the gate. I rode up on my 25 year old Miyata 610 and had no problem triggering the sensor. Sometimes we get ahead of ourselves with technology. (I showed the new employee where he could use his building key to open the gate.)

I find my aluminum road racer and my mountain bikes don't trip the inductive sensors. Both of my steel commuter bikes do a great job but there's the one intersection where I do need to drift over into the center of the lane to trip it.

On casual evening rides I often take the faster fair weather commuter. It's kinda hilarious watching all the lycra clad racer wannabe carbon snobs trying to track stand for minutes at a time until the precise moment when I or one of my other "steel is real" friends catch up.

not too much trolling in commuting. We should try to keep it that way. A&S is a cesspool full of trolling, and that really detracts from the forum. Never heard that about criticizing artists, I'll make a note of it.


I have heard that going down the center of the inductive loops is the best way to trigger them, but it doesn't usually work for me. I tried going down the loop today on the loop I would most like to trigger, but it didn't work either. No carbon here, I commute on a touring bike.

A) I don't think he was really trolling - trolls are just trying to make people angry - he was trying to make people think.

B) Center of inductive loop is NOT the best - you want to be on the wire. If it's a figure 8, then you drive on the center wire, which is sort of in the middle.

See:
http://www.humantransport.org/bicycl...nals/green.htm

also:
http://www.humantransport.org/bicycl.../detection.htm