Those speed detecting cables across the road.
Discussion
Being used for a speed survey on an NSL single carriageway A road.
Is it better to cross them below the limit to show that the current limit is working and doesn't need reducing,
or fly across as fast as possible because a few 100 mph measures will push up the 85th percentile and show that the limit shouldn't be reduced.
Just asking
Is it better to cross them below the limit to show that the current limit is working and doesn't need reducing,
or fly across as fast as possible because a few 100 mph measures will push up the 85th percentile and show that the limit shouldn't be reduced.
Just asking
When we used them the unit would log each vehicle movement, with a time, speed and vehicle classification (from bicycle to artic, based on vehicle weight and axle counts) - provided the installer lays the tubes accurately the speeds are accurate
We used them to measure actual speeds for road alterations, for example; a developer wishes to add an entrance to a road to his new housing development. The road is a 50mph limit, but traffic speeds are usually lower due to the road layout. The junction would normally require visibility splays to X metres in both directions in a 50mph zone, which the developer cannot achieve due to a wall on the neighbouring land, however by showing that vehicle speeds are lower than that in reality we can give reason for reducing the visibility required in this particular case
We also use them on larger development plans simple to measure traffic volumes, number of vehicles using particular routes, in order to ensure any new large scale development wouldn't overload the traffic network
We used them to measure actual speeds for road alterations, for example; a developer wishes to add an entrance to a road to his new housing development. The road is a 50mph limit, but traffic speeds are usually lower due to the road layout. The junction would normally require visibility splays to X metres in both directions in a 50mph zone, which the developer cannot achieve due to a wall on the neighbouring land, however by showing that vehicle speeds are lower than that in reality we can give reason for reducing the visibility required in this particular case
We also use them on larger development plans simple to measure traffic volumes, number of vehicles using particular routes, in order to ensure any new large scale development wouldn't overload the traffic network
Swervin_Mervin said:
Yeah, we use them for the very same purposes. But that doesn't mean they're that accurate
Perhaps I should say "accurate enough"... They're not scientific equipment by any stretch, but I tested a few of my own installations (out of curiosity and coincidence) and they were always within a couple of mph of my actual vehicle speed...
calibrax said:
It might be set to be accurate for an average car, but if you have an LWB car/limo or a van/truck/lorry then it will record much slower speeds than reality.
Speed is recorded by the time it takes for the wheel to pass over the first tube and the second, it's independent of wheelbase 
Remember though that although the cables across the road may not be used as a speed detection device they can be used to justify the use of speed cameras.
As in "we did this traffic survey along X road and found a large proportion of the traffic was exceeding the speed limit. We would like to put a couple of speed cameras along this stretch of road."
As in "we did this traffic survey along X road and found a large proportion of the traffic was exceeding the speed limit. We would like to put a couple of speed cameras along this stretch of road."
I'm afraid those cables are usually the harbinger of speed humps.
They'll often reinstall them after they've turned the road into an obstacle course to check that they've reduced speeds.
When they do this they will site them about a yard away from a speed hump; they don't like to be proved wrong!
They'll often reinstall them after they've turned the road into an obstacle course to check that they've reduced speeds.
When they do this they will site them about a yard away from a speed hump; they don't like to be proved wrong!
Drumroll said:
Remember though that although the cables across the road may not be used as a speed detection device they can be used to justify the use of speed cameras.
As in "we did this traffic survey along X road and found a large proportion of the traffic was exceeding the speed limit. We would like to put a couple of speed cameras along this stretch of road."
The double tube ones can definitely be used to gather data for justifying a change to an existing limit as well.As in "we did this traffic survey along X road and found a large proportion of the traffic was exceeding the speed limit. We would like to put a couple of speed cameras along this stretch of road."
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