Black lines

[5paul5]

Anyone know what the two black cables stretched across the roads are for ? Seems to be loads about in my area at the moment.

[Big Al.]

IIRC they are pneumatic sensors that trigger a counter when cars pass over them, so it would suggest they are measuring traffic flow.

[Lippy Kid]

I always assumed they were measuring the length of time it takes your wheels to runover the first one, to them running over the second one - thus detecting your speed.

I guess the info is used to gauge whether local traffic calming measures (cameras, warning signs, speed bumps etc) are needed.


But I could be totally wrong.

[Paulbav]

I think they are for monitoring traffic volume, maybe???

[Mr GrimNasty]

They seem to use pole camera versions around here now as the cables always got cut up and the boxes nicked.

[rampageturke]

Big Al. said:

IIRC they are pneumatic sensors that trigger a counter when cars pass over them, so it would suggest they are measuring traffic flow.

this is 100% correct

[BlueMR2]

They are gathering information in preparation of ruining the flow of traffic in you're area by spending loads of money to make it less car friendly.

[DaveH23]

Lippy Kid said:

I always assumed they were measuring the length of time it takes your wheels to runover the first one, to them running over the second one - thus detecting your speed.

I guess the info is used to gauge whether local traffic calming measures (cameras, warning signs, speed bumps etc) are needed.


But I could be totally wrong.

This is what i always thought aswell.

[Caesar9]

Lippy Kid said:

I always assumed they were measuring the length of time it takes your wheels to runover the first one, to them running over the second one - thus detecting your speed.

I guess the info is used to gauge whether local traffic calming measures (cameras, warning signs, speed bumps etc) are needed.


But I could be totally wrong.

I can't see how that would work though as a range rover will have a different distance between the front and rear wheels than a mini so each car will have a different time between the front and rear wheels at the same speed.

[Ari]

Two lines so time between front wheels running over first and second lines.

Irrelevant if Range Rover or Mini.

[PoleDriver]

Caesar9 said:

Lippy Kid said:

I always assumed they were measuring the length of time it takes your wheels to runover the first one, to them running over the second one - thus detecting your speed.

I guess the info is used to gauge whether local traffic calming measures (cameras, warning signs, speed bumps etc) are needed.


But I could be totally wrong.

I can't see how that would work though as a range rover will have a different distance between the front and rear wheels than a mini so each car will have a different time between the front and rear wheels at the same speed.

????? You wouldn't need to sense front and rear wheels! That's why there are two cables! Front wheels would hit cable #1 then cable #2, speed can then be derived from time taken. But they aren't used for that, they have cameras for that job.
One cable across the road can be used to measure total traffic flow, two cables can measure traffic flow in each direction!

[Mr Sparkle]

There is a type that measure speed by cables in the road, but there are 3 cables rather than two.

[Lippy Kid]

Caesar9 said:

I can't see how that would work though as a range rover will have a different distance between the front and rear wheels than a mini

I was thinking this:

Ari said:

Two lines so time between front wheels running over first and second lines.

However, it seems I'm wrong anyway...

PoleDriver said:

????? You wouldn't need to sense front and rear wheels! That's why there are two cables! Front wheels would hit cable #1 then cable #2, speed can then be derived from time taken. But they aren't used for that, they have cameras for that job.

[Caesar9]

Yup I've been proven wrong. I was thinking of the single lines which I'm guessing are traffic measuring.

Poledriver makes sense so I shall now go and hide.

[sebhaque]

After I saw a biker pop a wheelie over one of the black line things (which I believe are used to measure traffic flow, something tells me the recent surge of them is to do with priority for council gritting through the coming winter), I wonder what the box would record for wheelie girl/boy and random folks jumping on the cables.

[PoleDriver]

Caesar9 said:

Poledriver makes sense.

Nobody has ever said that before!

[Lippy Kid]

Hmm. Deleted post?



ETA: Quickly in, PD!

Edited by Lippy Kid on Thursday 20th October 23:48

[PoleDriver]

nixon1905 said:

PoleDriver said:

????? You wouldn't need to sense front and rear wheels! That's why there are two cables! Front wheels would hit cable #1 then cable #2, speed can then be derived from time taken.

You're sort of right! But to derive the speed you need to know the distance between the front and rear wheels as well, Speed = Dist/time. Basically its not possible with that particular cable set up and different lengths of cars going over the top!

For a two-cable system you are wrong! The front axle is going at the same speed as the rear axle! Front wheels will travel the fixed distance between the two cables in a certain time. Your equation can then be applied. It doesn't matter how far away the rear wheels are!

[sebhaque]

nixon1905 said:

You're sort of right! But to derive the speed you need to know the distance between the front and rear wheels as well, Speed = Dist/time. Basically its not possible with that particular cable set up and different lengths of cars going over the top!

I'm not sure! If the system is programmed to know the distance between the two cables, then a time log will reveal the speed of the car going over it with one set of wheels - the front wheels will hit the first cable, starting the timer, and then hit the second set, stopping it.

Speed is distance over time, so if the distance between the two cables is known then it's just a case of measuring the time taken between the first cable triggering and the second cable triggering.

ETA: damn slow fingers and overactive brain.

[twazzock]

sebhaque said:

I'm not sure! If the system is programmed to know the distance between the two cables, then a time log will reveal the speed of the car going over it with one set of wheels - the front wheels will hit the first cable, starting the timer, and then hit the second set, stopping it.

Speed is distance over time, so if the distance between the two cables is known then it's just a case of measuring the time taken between the first cable triggering and the second cable triggering.

That is assuming a standard distance between front and rear axle. A Fiesta and a lorry are going to provide vastly different results