Yeah I know these are used for counting vehicles but can they also be used for detecting vehicle speed?
Description: two pneumatic hoses, affixed to a road. They lead to a box that’s locked to a telephone pole. Location is southern California. On a minor artery road.
Doubtful that it’s to survey if a new stop sign is needed since the next street is minor, dead ends into this one and already has a stop sign. The next intersection with another minor artery already has a stop sign.
Extremely doubtful that a traffic light is being considered since there isn’t anywhere near the amount of traffic to justify one.
This is located on a slope. Many cars speed down here. That’s why I’m wondering about speed sensing by this device.
They are for counting vehicles. You cannot determine speed accurately without knowing the tire circumference
If you know the distance between the two tubes you could determine speed and not need to know anything about the tire.
Would they be able to account for the difference in length between each axle on different vehicles?
First hit on each would be the same tire and that’s all the information needed.
The circumference? Why would that matter? You have distance between the detectors and you have the time between their triggering. That’s enough to get a good estimation of the speed and direction of the triggering vehicles.
It’s for traffic count. IIRC the double track to is differentiate the count between passenger cars and semi-trucks (aka tractor trailers, 18 wheelers). The double track can differentiate when there are multiple axles like you see on semi-trucks. Sometimes you want separate counts.
You could calculate speed for shits and giggles but it’s not enforceable obviously.
It’s not for enforcement…this will tell them if they can ‘make profit’ by putting up auto ticketing systems that fine you when speeding.
They generally only use a single one for counts. You use the double setup here for speed tracking.
What I’m saying is they use a double to differentiate counts between passenger cars and semi-trucks (aka tractor trailers, 18 wheelers). Sometimes you want a count of 1) passenger cars and 2) semi-trucks. That’s what I remember learning it was for. I’ll edit my previous reply in case people are misreading it.
I always slow way down on these just to slightly skew the numbers. Though that could go good or bad for me, without a way to know.
If these had been around when I was a kid, I’d probably run over it a bunch of times with my bike. Especially going “backwards.”
I didn’t have any inside knowledge, but I can’t think of what having two would help other than the ability to measure speed. You can count just fine with one.
I should imagine you could measure direction too, if one is tripped before the other.
They may be for calculating speed, but without any further information, there’s no way of telling what wheels belong to what vehicle, or how many wheels (edit: or more specifically, axles) a vehicle has - so it certainly wouldn’t be viable for enforcement.
You can also estimate the size of the vehicle. based on how fast it it going and the time between front and back wheel you could calculate the distance between the wheels.
with two strips you can get a lot more data than if you just have one. count, direction, speed, size, and times the road is active. I dont know if they active measure all that but its possible.
That would be the problem for speed, but for counting you’d just look for close sets of pulses.
Oh, I somehow misread that as you saying you could get speed from just one
Yes, with two hoses they are measuring count, speed, and vehicle weight. Not enforceable, as many others have said - nobody will be getting a speeding ticket from this. It’s just data collection.
Note: force measured on the hoses is a function of vehicle weight and speed. If you only have one hose, you can’t tell the difference between a light vehicle moving fast and a heavy vehicle moving slow. With 2 hoses you can now measure speed, which you can then use along with the pneumatic force to figure out weight.
