Just for counting? For speed also?
Just for counting? For speed also?
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.
It's for a traffic study. For traffic volume and speed.
Depends on the state, but it's pretty common to to a speed study to see how traffic is flowing. This can result in adjusting the speed limit to match the majority of traffic. Or implement other traffic calming measures if a lower speed is required for some reason.
It could also lead to more enforcement I guess but where I'm from that's not its intended purpose.
97Just wanted to add that California in particular has a law requiring cities to study average speed before they change a speed limit. (And then have to pick a speed that 85% of traffic can follow, unless there are extra safety concerns.)
22You can often get out of a speeding ticket thanks to this, as it's pretty common for the traffic studies to be out of date or to have flaws that you can argue about.
6Oh yeah, I've heard of that law. 'Sure hope they don't raise the speed limit on this street!
2
Work at a city. Using these to lead to enforcement implies that city engineering is working with law enforcement and that level of coordination is… unlikely.
These kinds of lines are very engineering, very road design focused.
19In some cases they also check the axel length to determine the type of car. Not sure what that was used for.
3Also measures direction of course
3
They measure speed (how long between compression of each hose), direction (which hose was hit first), weight (how much was each hose squeezed), and axel count (how many pairs of wheels went over).
When you are calculating road wear, number of axels (and weight) is more important than number of vehicles.
You can often derive the number and type of vehicles by the pattern of “hits”. A passenger car will have a different pattern than an 18-wheeler; a van will have a longer wheelbase than a motorcycle, etc.
62It blew my kond ehen i foind oit that engineers won't even factor in cars when designing major bridges because they are essentially a rounding error compared to semi-trucks.
43
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.
58They could be measuring direction also
5
This sent me down a rabbit hole, now I'm reading a manual on how to calculate the data.
For those interested: https://www.fhwa.dot.gov/policyinformation/pubs/pl18027_traffic_data_pocket_guide.pdf
30Allow me to share some personal experiences when setting those up. Nimby's would approach us and rant about how we were only there to justify a new stop sign or speed bump. A few times we were approached by ding dongs wielding weapons. And every once in a while people like to sabotage or steal the equipment. But once they tamper with the equipment enough times they basically get put on the shit list so their road doesn't get serviced they don't get plow service they don't get anything. Maybe this was their goal maybe not who knows they're idiots.
Honestly, highway data is used for all kinds of things but mostly for planning repairs, upgrades, and modifications. Redesigning things like intersections, traffic lights, and stop signs are rarely the result of this sort of highway data collection. It's reported collisions and fatalities that drive safety interventions.
But again, we're talking about nimby's who are all fucking idiots.
8Since I have neither the time nor the inclination to read it, but I do have a question- can you answer it? Quit record if you just jumped on it? Or you and like five friends?
5Pretty sure it'll be seen as noise and ignored. The algorithms aren't perfect but they're pretty tight and look for specific things. Unless you can emulate with a reasonable level of accuracy what is looking for it'll just ignore what you do.
8There's a timing tolerance you can program. So if you only want to count double axles or get the speed data based on a presumed axle spacing, you can program that in. But, if you feel you must spoof it, listen to the sets of tires as they cross the hose and match that timing while stomping on the hose. You need to stomp pretty hard to get the hose to compress enough and you need to generate an air hammer pressure wave within the hose. This and the intensity is what is measured by the device and recorded as an event.
But these modules are left for weeks to months. So if the counts are all in the, let's say, 300 range daily but then one single day shows 1000, that day's data is typically removed from the set. Outliers can happen for all kinds of reasons (e.g. failure, hose break, weather, loss of solar power, unusual or atypical activities, children young and old). So, if the counts are wildly different than prior years' counts, daily/weekly/monthly inconsistent, beyond comprehension, or obviously defective; they can set up more than one device if they need and some devices can receive more than one input. They can also program the device with multiple inputs to only record data within a specific range of parameters. So there are lots of ways to limit the shenanigans in the data.
And you'd be surprised at how much traffic some roads get. Even some residential roads would see thousands daily. So if you really want to bump up the priority of the road, you would be better off driving over it all day, every day until it was removed; because you'd destroy your leg trying to stomp on it that many times. And you'd have to do this on all adjacent and feeder roads to support that data. And you'd have to ensure that you do this every year until you recognize the desired effects of your endeavor, and then you'd have to continue this practice in perpetuity. Or the jig is up!
4Drive over it very slowly a few hundred times
3
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.
28I 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.
54You 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.
24Good point about direction. I couldn't imagine using this for enforcement, but I'm guessing you could be pretty confident any the number of axels but counting the ones that are the exact same speed and by the distance apart.
7
I have seen cases where two tubes are used, but one only stretches half way, so they can tell which lane is used.
5Weight, since if you don't know speed you don't know if it's light and slow or heavy and fast. Number of vehicles, since you can't count axles without the above data
2How would you calculate speed, with just one cable?
1
My question is whether they count bicycles. And are able to detect them as such.
7We have these on bike lanes at intersections in the Netherlands.
In addition to everything already discussed here, they also have the role of asking for a green light automatically for you. If there are no cars travelling on Street ways contending with the bike lane, the light turns green. Alternatively, it turns green when you get your turn.
You can also ask for the green light by pushing a button, but it's nice that some intersections (the newer ones) don't require it.
However, I'm not sure if these can be configured to work for both cars and bikes at the same time.
2
A great use of my time while I wait for my flight that's been delayed by 5 hours!
6
Looking at the road, it might be to make a call on which road to repair/patch in the near future based on usage if the budget doesn’t allow repairing all (it never does).
Once water gets into the cracks, things deteriorate a lot faster as the ground will push and pull asphalt around as it gets wet and dries up…
10Where I'm at, there are "speed vans", these survey boxes are also used to determine where the speed vans should be placed, though the other uses such as vehicle weight/axle count others mentioned are the main function afaik.
These speed vans are equipped with cameras that can capture several lanes and directions, from a great distance. You just drive past these things and they have a sign on top saying "your speed has been checked".
8I don't know for sure, but I think theoretically you could calculate the time it takes between a tire driving over each line to determine the vehicle speed. I imagine that's why there are two lines and not just one.
5They're usually not used for speed where I live. They're simply for measuring traffic.
I can think of a few situations where it is used on small roads only to check the traffic without it necessarily meaning that any changes will be made to the small road.
If someone owns a small private road which is open to public traffic and it gets used a lot by people who don't live on that road, it's possible to request a reading of how much traffic passes through to determine if the municipality should take over responsibility of maintaining the road.
If there recently was built a larger bypass it makes sense to check if people still use the smaller roads instead of the bypass for whatever reason.
These things can be used to figure out lots of other stuff about traffic dependent on how and where they're set up, but generally it's that kind of thing. Just traffic measurement.
Speed readings would be incredibly annoying to do this way. While it is technically possible, most of the data would be useless. Sorting through data from several weeks only to be able to determine that someone probably speeded there last week doesn't really give any meaningful information to anyone.
Speed checks are better done with the sort of doppler measurement devices that you might know from the signs that show your speed and blink when you're speeding.
2There's almost no reason for having two of them other than to measure speed, otherwise you'd only use one. But it's not for enforcement, it's to see how fast most drivers actually drive the road. This can be used for things like adjusting the speed limit, or testing to see if measures need to be taken to enforce it more strictly, etc. I know there is a hill in my hometown that residents used to always complain about speeding. They used exactly this setup to track the speed of drivers. They found that there was no excess in speeding, the steep hill required more gas to maintain speed, and people generally associate louder engine noise with higher speed.
5There's two of them to determine the direction.
1
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."
2It'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.
0They generally only use a single one for counts. You use the double setup here for speed tracking.
2What 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.
2
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.
2Yes it's not for enforcement, that's why I said it's not enforceable. And that it's for traffic counts.
4
They are for counting vehicles. You cannot determine speed accurately without knowing the tire circumference
-10The 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.
20Yeah I mixed up the knowledge of how wheel size impacts speedometer accuracy with this
Whoops
3
By that logic, you cannot tell how fast I'm walking without my circumference.
17How does the circumference matter?
6It does not. Circumference only tells you speed if you're measuring tire rotations, which this is not.
4
