What are the twin cables sprawled across our roads for?

[Isiris 10]

Really

 

It makes no distance whether its a hgv, a boat or a cyclist.

 

You go over the first line, time on, then go over the second line, time off. Time calculates speed over measured distance.

 

Same as how average speed cameras work. The cameras point to a calibrated point on the road and register how long it was since the number plate was on a calibrated point, some distance back

[blowfealt 10]

Really

 

It makes no distance whether its a hgv, a boat or a cyclist.

 

You go over the first line, time on, then go over the second line, time off. Time calculates speed over measured distance.

 

Same as how average speed cameras work. The cameras point to a calibrated point on the road and register how long it was since the number plate was on a calibrated point, some distance back

 

Are you sure?

 

A boat has no wheels (steering wheel does not count), a HGV has multiple sets.

 

There is no camera in this set up as far as I am aware, though it might be the way forward to collect accurate data?

[montie 10]

They are pneumatic road tubes as per this extract off t'internet:

 

"A traffic counter is a device, often electronic in nature, used to count, classify, and/or measure the speed of vehicular traffic passing along a given roadway. The device is usually deployed in near proximity to the roadway and uses an on-road medium, such as pneumatic road tubes laid across the roadway, piezo-electric sensors embedded in the roadway, inductive loops cut into the roadway, or a combination of these to detect the passing vehicles. Pneumatic road tubes are generally used for temporary studies to study a sample of traffic, while piezo-electric sensors and inductive loops are used for permanent studies which can ascertain seasonal traffic trends and are often used in congestion monitoring on major roads."

 

---------- Post added 22-06-2015 at 20:32 ----------

 

 

Not if you allow yourself to think about it.

The Council pays for it directly or through the likes of Amey.

They will have their own reasons for temporary or short-term monitoring of traffic flows, direction, speed, density.

Anything longer term is dealt with by other more permanent (and more costly but more durable) technologies (also mentioned in this extract).

Be wary of rushing to criticise the Council.

 

'Be wary of rushing to criticise the Council'...steady on there, that sort of attitude will get you drummed out of Sheffield Forum

[jane2008 15]

Hi, anyone who cruises the streets in the South East of the city will have noticed twin cables sprawled across the street at regular intervals, usually tethered to a lamp post.

 

There is some kind of box attached adorned with a logo, but I have not yet found a suitable situation/location to stop and inspect the device.

 

Are they some kind of speed trap or stinger, or are they some kind of data collection device?

 

We had these on our local roads a few months before they introduced a 20 mph speed limit. I don't know whether that is a coincidence or not

[Camrat78 10]

Are you sure?

 

A boat has no wheels (steering wheel does not count), a HGV has multiple sets.

 

There is no camera in this set up as far as I am aware, though it might be the way forward to collect accurate data?

 

It doesn't matter how many sets of wheels it has. It calculates the time from the first axel going over the first wire to it going over the second. Its not to try to catch people, but so they can get a rough idea of the sort of speeds people are doing to see if traffic calming measures are needed.

[the_bloke 17]

Your figures are fudged. Apply them to a HGV.

 

They aren't fudged at all, they are realistic - actually, a lot of cars have a wheelbase less than 3 metres, so that 0.2 seconds is even less.

 

If you want to extend it to HGV, then sure. An articulated max length in the UK is 16.5m, so I have no idea what the wheelbase is. We'll run with that anyway:

 

Time = Distance / Speed

Time = 16.5 m / 13.41 m/s

Time = 1.2 seconds

 

So again, how much speed do you expect to lose or gain from 30 MPH in an HGV in 1.2 seconds?

 

In practice it would be less than 1.2 seconds, as the wheelbase is less and our articulated lorry doesn't just have two axles, it has six to roll over the cables. So, six measurements in 1.2 seconds.

[blowfealt 10]

They aren't fudged at all, they are realistic - actually, a lot of cars have a wheelbase less than 3 metres, so that 0.2 seconds is even less.

 

If you want to extend it to HGV, then sure. An articulated max length in the UK is 16.5m, so I have no idea what the wheelbase is. We'll run with that anyway:

 

Time = Distance / Speed

Time = 16.5 m / 13.41 m/s

Time = 1.2 seconds

 

So again, how much speed do you expect to lose or gain from 30 MPH in an HGV in 1.2 seconds?

 

In practice it would be less than 1.2 seconds, as the wheelbase is less and our articulated lorry doesn't just have two axles, it has six to roll over the cables. So, six measurements in 1.2 seconds.

 

It takes a real man to admit he has made a mistake. I respect you for that.

[the_bloke 17]

It takes a real man to admit he has made a mistake. I respect you for that.

 

I haven't made one, however I've enjoyed teaching you pre GCSE level applied maths.

 

At least you've learnt that these two cables can measure speed now.

[blowfealt 10]

It doesn't matter how many sets of wheels it has. It calculates the time from the first axel going over the first wire to it going over the second. Its not to try to catch people, but so they can get a rough idea of the sort of speeds people are doing to see if traffic calming measures are needed.

 

Thanks, but is a "rough idea" sufficient to commit serious money to address the "findings" of these technically incorrect surveys?

 

Makes you wonder.

 

---------- Post added 22-06-2015 at 22:10 ----------

 

 

you've learnt that these two cables can measure speed now.

 

Yes I have. Thank you.

[Haydn1971 10]

The twin tubes are for classified counts that each local and national highway authority collects on behalf of the DfT to feed into the funding settlements for capital and revenue funding.

 

You can use tubes for speed, but this time of the year, they aren't collecting that data specifically but use speed to help classify what's gone over the tubes - not sure how the boxes work to be honest, but what we get is a traffic count of different vehicle types. Showing different wheelbase type numbers, for example cycles, car & car based vans, 3.5t, 7.5t etc etc etc.... From the counts the DfT calculates traffic volume across a highway authority and pumps it into the spreadsheet that splits the maintenance budget up across the country. The data is often also used to help us engineers do feasibility stage design, then validate later with specific counts for links and turns.

[iansheff 88]

We had these on our local roads a few months before they introduced a 20 mph speed limit. I don't know whether that is a coincidence or not

 

Haven't they made all non main roads 20 mph?

[melv 16]

The twin tubes are for classified counts that each local and national highway authority collects on behalf of the DfT to feed into the funding settlements for capital and revenue funding.

 

You can use tubes for speed, but this time of the year, they aren't collecting that data specifically but use speed to help classify what's gone over the tubes - not sure how the boxes work to be honest, but what we get is a traffic count of different vehicle types. Showing different wheelbase type numbers, for example cycles, car & car based vans, 3.5t, 7.5t etc etc etc.... From the counts the DfT calculates traffic volume across a highway authority and pumps it into the spreadsheet that splits the maintenance budget up across the country. The data is often also used to help us engineers do feasibility stage design, then validate later with specific counts for links and turns.

 

As I said in post No2. They count traffic:hihi: