Ropes across the road in Cork

ageary08

Hey, Does anybody in cork (maybe there nationwide !)know what those ropes across the road are ? they appear to be bolted down at once side and the other side is attached to some kind of metal box. Iv seen them on the link and a few around togher. I have a few fun theorys on what they are myself

- Traffic counters, every time something runs over the set of ropes it counts it, then divides by two or what ever to figure out the number of cars passing

- Some kind of cunning terroist plot involving giant claymores

- Arrestor cables, like ya know on aircraft carriers

PS. for anybody not in cork, im not on crack, srsly

L1011

Traffic counters.

mikemac

ageary08 wrote: »

- Traffic counters

You answered your own question

ageary08

Ok, thats most of the fun sucked out of it. Im guessing these are just for short term use, is it the dept of transport or something ? I wonder how they deal with multi axle trucks and such.

5uspect

I suppose they use them for gathering statistics about road usage for planning (aparently it does happen in Ireland!)

Regarding multi axle vehicles I'd imagine they would look at the frequency of the signals recorded and determine the number of axels from that. Pulses within 0.01 seconds of each other would count as one vehicle for example.

AugustusMaximus

Where on the South Link Road ?

I use the road every day and never seen them.

Alun

There is some fairly sophisticated post processing software they can use to analyse the results from these things and determine the types of vehicles and speeds. There was a thread on this subject a while ago and someone posted a link to a company in the UK that made these boxes and the accompanying software.

Wishbone Ash

Alun wrote: »

the results from these things and determine the types of vehicles and speeds

I don't think they can measure speed. AFAIK the reason that there are two cables is to determine the direction of travel, i.e. the direction can be determined by the cable which is struck first.

5uspect

Surely they should be able to measure speed reasonably well if there's two cables?
Speed = distance x time, just cross correlate the two time traces and you get your time lag. It would all depend on the sampling frequency and response of the systemt tho.

Victor

They are aparently air tubes, the device record each time the air flow is interrupted. However, I suspect this isn't enough to measure speed. There are other devices used to do that.

AugustusMaximus

To be able to measure speed you would have to know the distance between the two axles for each car.

Of course, this is obviously impossible.

Victor

AugustusMaximus wrote: »

To be able to measure speed you would have to know the distance between the two axles for each car. Of course, this is obviously impossible.

Depending on your sensor, you could merely use the amount of time that the front wheels pass each tube (the are placed maybe 500mm apart, but it is probable that this isn't scientific). This could be repeated for the rear axel to get an average.

Of course laser, radar or video devices are more suited to this.

5uspect

if there are two independent tubes then both tubes will see the same thing only slightly out of sync. Assuming traffic is only going one direction (it would work for both ways too but the maths gets messy!) then the logged data from both can be correlated to find the time lag. Using this time and the distance between the tubes you get the average speed of the traffic.

If you calculate the time difference between each vehicle event, which would require conditional sampling, then you could get the speed of each car.

Signal analysis is fun!

Capt'n Midnight

The very old kind has an air filled rubber tube. When a wheel hits it a puff of air blows some sand from a resevoiur into a jar.

One tube goes across the whole road , the other half way across. Weighing the sand gives you the total traffic.

corktina

One set is at the Togher exit on the city side near the roundabout....

L1011

The new kinds are attached to very ruggedized computer equipment in a very big box usually thrown in the bushes near where the counter is. Have seen one of the boxes open when they were doing the counts in Maynooth to try to figure out how the hell to reconfigure the main street...

Wishbone Ash

MYOB wrote: »

The new kinds are attached to very ruggedized computer equipment in a very big box usually thrown in the bushes near where the counter is

The box is often chained to a lamp post also.

Heard story a few years ago when a traffic counter was set up on an A road just outside Northampton.

They determined the type of vehicle (no of axles) by the number of pulses within a given timeframe relative to the time between the first pair of pulses.

It appeared that something like 30% of the veticles had six axles!! A follow up visual survey reported severe problems with tailgating.

Victor

5uspect wrote: »

Signal analysis is fun!

Nerd!

I saw two sets, one on North Douglas Road (two way) and the other just before the train station (one way). At the train station, there was two tubes, not connected at the right end and presumably only a device at the left end (I couldn't see that point).

Capt'n Midnight

Wishbone Ash wrote: »

The box is often chained to a lamp post also.

where could you sell a stolen counter ??
then again that's the sort of world we live in

Deleted User wrote: »

It appeared that something like 30% of the veticles had six axles!! A follow up visual survey reported severe problems with tailgating.

Forget speed cameras this looks like a winner - set it to 5 axles in Dublin and nail those flouting the €5 congestion fee (reg / date don't match issued permits ) / tailgating

- would also be easy to set it up for a 1 second / 2 second in the wet rule

godtabh

Capt'n Midnight wrote: »

where could you sell a stolen counter ??
then again that's the sort of world we live in

They get vandalised allot as well.

We've had some destroyed recently.

Victor

I've seen the recording unit on some equipment stuck more than "two drunks high" up a lamp post.

Dont be at yourself

I think some of them, at least the ones buried in new bypasses and such, work on the principle of induction and can estimate the type of vehicle etc.

5uspect

A guy here in work rigged up an old protected suspension bridge down under with fibre optic bragg gratings that allow strain measurements (when you compensate for temperature. Its purpose was to monitor the bridge in order to preserve it.

Basically they were able to tell the weight and speed of vehicles passing over the structure from their load on the supporting cables. Since the structure is protected HGVs aren't allowed onto it and the system was able to detect them in real time.

deRanged

Victor wrote: »

t the train station, there was two tubes, not connected at the right end and presumably only a device at the left end (I couldn't see that point).

I was looking at that this morning.
At the base of the lamp post there's whatever box is attached. I wonder how long it'll last there. I'll grab a photo tomorrow if anyone's interested?

godtabh

NekkidBibleMan wrote: »

I think some of them, at least the ones buried in new bypasses and such, work on the principle of induction and can estimate the type of vehicle etc.

They are usually used to detect the presence of a car to trigger lights and estimate queue lengths.

The UTC can detected speeds, vehicle types, counts etc.

deRanged

the magic box near the train station in cork.

L1011

Appears to be: http://www.metrocount.com/products/mc5600/mc5600series.html

Have seen those used here but also seen far larger units.