black wire on road, what is it?

[Rubba Burna]

its always been on my mind but i never got to it til now. usually on high ways, i see a black wire taped down across the road. i coudnt find pics cuz idk wtf it is. is it something that surveys the speed of the cars? sometimes i even see two wires, 2 or 3 feet from each other. When the car goes over it, you can hear a little "cluck" and feel it too. anyone know what im talking about? thanks in advance

[gimme]

it's a traffic survey

[Yes, I Vtec]

ya it just sees how many people go through the intersection or whatever so they know how busy areas are

[stevet47]

I think when it is 1, it counts vehicles, when it is 2 it checks speeds.

[kylerwho]

the check speed thing would be inaccurate cause a motorcycle's two wheels would run over it quicker that a extended cab truck would therefore showing that the bike was traveling crazy fast.

[spreadhead]

Originally Posted by kylerwho

the check speed thing would be inaccurate cause a motorcycle's two wheels would run over it quicker that a extended cab truck would therefore showing that the bike was traveling crazy fast.

As stevet47 said to check speed a two wire setup is used. The device measures the time between the front tire crossing the first wire until the time that the front tire crosses the second wire. This is very accurate.

[kylerwho]

i repped you for that little piece of information.

[MookHustle]

just liek they said, 1 is for number of vehicles, 2 is for speed.

[mikejet]

So if I see a single wire and put bricks on it roughly equivalent to the width of tires on a car will they think there is horrible traffic congestion?

[Rubba Burna]

yup, but i think they would check for malfuntions on the wire

[gimme]

Originally Posted by spreadhead

As stevet47 said to check speed a two wire setup is used. The device measures the time between the front tire crossing the first wire until the time that the front tire crosses the second wire. This is very accurate.

kind of along kyler's post...

how can they differentiate between a motorcycle to a car, car to truck, truck to rv, rv to semi? Too many factors like a truck for example: crew cab short bed has a longer wheel base than a standard cab short bed. I dont think it can accurately gauge speed.

I could be wrong...but it doesn't make sense to me

[TaffetaWhite]

Originally Posted by Rubba Burna

its always been on my mind but i never got to it til now. usually on high ways, i see a black wire taped down across the road. i coudnt find pics cuz idk wtf it is. is it something that surveys the speed of the cars? sometimes i even see two wires, 2 or 3 feet from each other. When the car goes over it, you can hear a little "cluck" and feel it too. anyone know what im talking about? thanks in advance

Automatic Traffic Recorders and/or Traffic Analyzers (those are the keywords to use in a search).

Here's a break down of what those things can pick up (one manufacturers model):
Automatic Traffic Recorder ATR Traffic Recorders at MetroCount the Traffic Data Specialists. Automatic Traffic Recorder ATR for Vehicle Traffic Monitoring and Recording of Vehicle Traffic.

Many of the sections have pdf sample pages to show what the data would look like...if we spoke French.