Not important but one of those things I've wondered about.
You know those automatic traffic counters the councils use, box at the side of the road, two rubber tubes across the road. Tyres crossing the tubes presumably cause some sort of counter to operate.
When the tubes go all the way across the road, how do they sort out how many vehicles have gone in which direction, or don't they bother? Also is a multi axle truck counted as several cars or what?
I know the answer has got to be simple but anybody any idea?
|
IIRC (my wife used to do traffic counts) a single tube counts traffic and they average the number of axles. They are therefore not dead accurate but if a proper count/avalysis is requires it is done manually.
A manual analysis is quite comprehensive, splitting into e.g. motorcyles, cars/light goods, medium goods, heavy goods(by axle number), public transport etc.. Good fun on the M25 in the rush hour, but actually more difficult in stationary/crawling traffic, you tend to lose your place.
Another variation on roundabouts is to have a team with tape recorders dictating the registration numbers of vehicles entering and ones on the exits doing the same. Back at the office the entries and exits are matched so that they can tell where the traffic flow is coming from and going to.
Double tube set-ups are to measure traffic speed, not numbers.
|
Thanks Brian,
Now follow up question.
"Double tube set-ups are to measure traffic speed, not numbers."
One I'm thinking of is a double tube one, and as its in Worcestershire, one of the most speed hating counties I've come across, I wouldn't be a bit surprised if it is speed related.
I can imagine a situation where opposing traffic crosses the tubes at about the same time. I bet they can get some funny results then. I assume these are then excluded as being non representative, or ... ??
|
>>Worcestershire, one of the most speed hating counties I'vecome across,
Oxfordshire or Gloucestershire?
--
Parp, Parp!
Note: All Toad posts come with an implied smiley.
|
|
I know more about the manual side than the mechanical, but I think that you will find that conflicting results are discarded and the mechanism resets itself.
These things are only used to gather data on traffic flow and speeds for the traffic engineers to plan alterations to road layouts, speed limits, road signs etc..
You also, of course, get the interviews where drivers are stopped and asked their starting and finishing points, for the same purposes.
|
|
I know this is an old thread but if anyones still interested:
"Double tube set-ups are to measure traffic speed, not numbers."
This is not strictly true, you can get a volumetric count by direction from a double tube set up. Typical spacing would only be about 3 and a half inches between the two tubes. This type of survey only counts axle pairs. This is then compensated for in the analyis.
In order to get a classified count a two tube setup must be used with a typical spacing of 1 metre between tubes. A classified count can be either or a combination of speed, class and gap.
"I can imagine a situation where opposing traffic crosses the tubes at about the same time. I bet they can get some funny results then. I assume these are then excluded as being non representative, or ... ??"
If this occurs then it can produce a false reading..........particularly busy roads should be monitored by lane/direction to avoid crossing vehicles.
Hope this clears up any concerns!!!
|
when were kids we used to do a wheelie over one of those counter things and spend the next tenty minutes grinning when the machine counts up an odd number
oh how we laughed.
|
unfortunately trucks frequently have an odd number of axles.
We used to jump up and down on them a lot; dunno if that worked either, but it used to keep us amused for minutes at a time.
|
pink fluffy dice
|
Some traffic counter units can monitor traffic flow levels, traffic speeds, carbon monoxide (CO) levels and ambient air temperature; models produced by American company Nu-Metrics can also measure vehicle length and speed.
Plymouth council conducted surveys for Road Traffic Reduction Act purposes:
tinyurl.com/4l6rz
My local council recently resurfaced (well asphalt and chippings to be honest so as to well and truly wreck paintwork and keep many drivers off such stretches for a while!) several roads and immediately put down traffic counters.
No doubt surprised by the results...:-))
|
|
|
we used to cut the pipes , that was fun as a kid , would'nt do it now though (older and supposedly wiser).
|
|
|
|
|