Rubber tubes across the road
Discussion
When you see thin rubber tubes across the road, I've always understood that one by itself is to measure the number of vehicles passing (by counting axles then dividing by 2 or 2 point something to factor in multi-axled vehicles), and two together is to measure the speed of vehicles (by providing raw data of time between axle crossing tube 1 and tube 2 to give speed) for possible future speed limit alterations or other measures (i.e. installation of speed cameras/road humps).
Because of this, I always tend to treat the two together like a speed camera by making sure I'm at or under the limit, so hopefully the powers that be will think there is no need for meddling with a perfectly good road. Am I informed correctly, and does anyone else do this?
Because of this, I always tend to treat the two together like a speed camera by making sure I'm at or under the limit, so hopefully the powers that be will think there is no need for meddling with a perfectly good road. Am I informed correctly, and does anyone else do this?
stooz said:
the distance between your axles could not be used in the calculation
ie a limo, and twin axles of a truck would report different speeds.
The only thing they could effectively measuer is the GAP between impressions, and there graph out congestion.
Yes it could, because it is measuring the time for one axle to cross both tubes (when in pairs they are typically around 12 inches apart). A car travelling normally will give a signature something like:
*Impression* (as front axle crosses tube 1) - very short gap - *impression* (as front axle crosses tube 2) - slightly longer gap - *impression* (as rear axle crosses tube 1) - very short gap - *impression* (as rear axle crosses tube 2). By looking at all raw data following this pattern they can calculate the speed of the vehicle from the two 'very short gaps'.
I'd put my vote up for two tubes being for direction. Or at the very least, *rough* indication of prevailing speed.
You couldn't use it for prosecuting someone for a speeding offence because the single tube runs across two carriageways. It's possible for you to pass tube one, and another car on the other carriageway to pass over tube 2 (tube 1 in their direction of travel) with a time difference indicating a speed much higher than the vehicles are travelling at in reality.
As I see it, they are used to track traffic patterns. You can tell the number of vehicles, direction of vehicle and size of vehicle (larger vehicles will cause greater changes in pressure).
Having so clearly nailed my colours to the wall, I will now wait to be shot down in flames.
You couldn't use it for prosecuting someone for a speeding offence because the single tube runs across two carriageways. It's possible for you to pass tube one, and another car on the other carriageway to pass over tube 2 (tube 1 in their direction of travel) with a time difference indicating a speed much higher than the vehicles are travelling at in reality.
As I see it, they are used to track traffic patterns. You can tell the number of vehicles, direction of vehicle and size of vehicle (larger vehicles will cause greater changes in pressure).
Having so clearly nailed my colours to the wall, I will now wait to be shot down in flames.
AlexH said:
When you see thin rubber tubes across the road, I've always understood that one by itself is to measure the number of vehicles passing (by counting axles then dividing by 2 or 2 point something to factor in multi-axled vehicles), and two together is to measure the speed of vehicles (by providing raw data of time between axle crossing tube 1 and tube 2 to give speed) for possible future speed limit alterations or other measures (i.e. installation of speed cameras/road humps).
Because of this, I always tend to treat the two together like a speed camera by making sure I'm at or under the limit, so hopefully the powers that be will think there is no need for meddling with a perfectly good road. Am I informed correctly, and does anyone else do this?
DS2 or Truvelo as used by police in speed traps requires 3 rubber tubes. When two tubes are seen, these are usually used by local authorities to measure speed, direction and numbers of vehicles.
One tube? Dunno. See www.ukspeedtraps.co.uk for more on Truvelo. Roll down index on the left of page to locate.
On the basis many of the "two tube" rigs are set up adjacent to change of speed signs, I'd say it's a safe bet they are measuring speeds with a view to future speed enforcement. One location near to my house is where the speed limit goes from 40 to 60. Guess which side of the sign they'll be measuring the speed?
DAZ
DAZ
Speed = distance divided by time
So if you cover the 12inch gap (between the two pipes) in 2 seconds, then speed = 12/2 = 6
(or something!)
The equation is correct though.
Apparently they are called Archers, and they monitor traffic speed - therefore if between the hours of 10pm and 11pm, there are consistently a lot of speeding drivers, theyll stick a speed trap there at that time, rather than over a 24hour period - more efficient, no?
So if you cover the 12inch gap (between the two pipes) in 2 seconds, then speed = 12/2 = 6
(or something!)
The equation is correct though.
Apparently they are called Archers, and they monitor traffic speed - therefore if between the hours of 10pm and 11pm, there are consistently a lot of speeding drivers, theyll stick a speed trap there at that time, rather than over a 24hour period - more efficient, no?
Mad Dave said:
therefore if between the hours of 10pm and 11pm, there are consistently a lot of speeding drivers, theyll stick a speed trap there at that time, rather than over a 24hour period - more efficient, no?
Exactly, which is why I treat them as if they were a speed trap; I realise they are not, but may lead to one...
superlightr said:
I though that the faster you drove over them then the more the 85 % rule would move up.
That's an interesting idea. I somehow get the impression though that the 85 percentile hasn't been used to set a speed limit in decades. Satisfying the vocal minority of thinkofthechildrenistas with politically set limits is much more effective for local government ('s protection of their positions of power).
If laid right across the road two tubes record the time at which each of the two tubes is compressed by the tyres of a vehicle passing over them.
Later analysis of the records give speed and direction on the basis of the time between the compressions (for speed) and whether the compressions are 1-2 or 2-1 (for direction).
Clearly there will be 'issues' raised by vehicles travelling roughly simultaneously in opposite directions, but over a long period these are statistically insignificant.
Generally the tubes are only laid right across lightly trafficed roads, and either independently on either side or only on one side for more heavily trafficed roads.
Streaky
Later analysis of the records give speed and direction on the basis of the time between the compressions (for speed) and whether the compressions are 1-2 or 2-1 (for direction).
Clearly there will be 'issues' raised by vehicles travelling roughly simultaneously in opposite directions, but over a long period these are statistically insignificant.
Generally the tubes are only laid right across lightly trafficed roads, and either independently on either side or only on one side for more heavily trafficed roads.
Streaky
I ignore 2 tubes across the road but 3 means there is a camera on the end of them. Usually standing on a tripod whilst the operators loiter nearby. This is what they did in Nottingham for quite a while until they got hand held equipement and the 'bottle' to use it. I haven't seen 3 tubes for a while. Last time I saw them I braked as hard as I could whilst going over them 
Boosted LS1 said:If you're referring to the DS2/TSS system, the "three tubes" are in fact (usually) electrical sensors buried in the road surface, not laid on top and stapled down - as is the case for the pneumatic sensors used for speed (and singly for traffic density) calculations.
I ignore 2 tubes across the road but 3 means there is a camera on the end of them. Usually standing on a tripod whilst the operators loiter nearby. This is what they did in Nottingham for quite a while until they got hand held equipement and the 'bottle' to use it. I haven't seen 3 tubes for a while. Last time I saw them I braked as hard as I could whilst going over them
AlexH said:
therefore if between the hours of 10pm and 11pm, there are consistently a lot of speeding drivers, theyll stick a speed trap there at that time, rather than over a 24hour period - more efficient, no?
Exactly, which is why I treat them as if they were a speed trap; I realise they are not, but may lead to one...
Thats what I think too, and hence I always slow for them. On occasions much to the fury of the guy behind who can find themselves suddenly 2 inches from my back bumper and their nose squeshed on the windscreen!
Chrisgr31 said:From what I have been told by friends in the motor insurance business, in the event of a shunt, the driver of the lead vehicle might have to provide a valid reason for suddenly slowing. But I do the same - Streaky
Mad Dave said:
therefore if between the hours of 10pm and 11pm, there are consistently a lot of speeding drivers, theyll stick a speed trap there at that time, rather than over a 24hour period - more efficient, no?
Exactly, which is why I treat them as if they were a speed trap; I realise they are not, but may lead to one...
Thats what I think too, and hence I always slow for them. On occasions much to the fury of the guy behind who can find themselves suddenly 2 inches from my back bumper and their nose squeshed on the windscreen!
streaky said:
From what I have been told by friends in the motor insurance business, in the event of a shunt, the driver of the lead vehicle might have to provide a valid reason for suddenly slowing. But I do the same - Streaky
Well as Direct Line seem not to offer legal protection for speeding relating cases I guess a cat or dog ran across the road!
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