square cutouts in the road (no pic sorry)

ZygOte

first of all i dont have a pic sorry!

has anyone else noticed when your driving along the road (mostly on motorways) there are often what look like two squares in the road in each lane side by side. they look like a piece of the road has been cut out and then glued back in again, there is always a black glue type boarder around them , you often see them near on and off ramps on the M50.

anyone know what and if these are anything at all? is it just pipes under the road or is there something else going on there?

colm_mcm

these usually coincide with overhead signs. there's usually one before and one after.

stratos

These are traffic volume monitors. A channel is cut in the road and a loop (induction loop) of cable is buried in it. the channel is filled in with bitumen. every time a metal object (Vehicle) passes over the loop it causes a change in the current flowing in the loop. this current is monitored by a nearby computer and the volume of traffic is monitored.

colm_mcm

I'm not certain these are induction loops. they're always within a few metres either side of overhead signs (the ones I've seen anyway)

ian_m

You can also see them in front of traffic lights. I purposely make sure I drive onto the box to get the lights to change.

endplate

Near traffic lights they are traffic sensors to instruct the lights to change to allow freeflow as much as possible. I think that the traffic light IT group are unaware how to set these up as they never seem to work

rebel.ranter

I remember a brief discussion in college where the lecturer mentioned that traffic planning & management an be done by using these type of sensors. They can be used to manage traffic volumes, peak traffic times, etc. In theory they should be used to beeter manage our traffic, determione when new roads shoudl be built, off ramps etc. Traffic management is a science, how to plan the sequences of lights along a route (e.g. through a city centre) but I don't think we in Ireland have invested too heavily in it. It seems to be a bit more like trial & error.

peterd

I assume these could be the same as the ones used at traffic lights in dublin city just before the white stop line - they're inducion coils. If you're driving at night around the city and there aren't any other cars on the road, roll up to a red light and stop your car right on the boxes, the lights should change for you almost instantly!

CrowdedHouse

There's a couple of yokes on the N7 near Borris in Ossory,first time I saw them I thought it was a lost mudflap.Later I noticed there was one at each side fixed to the road.No traffic lights('cept pedestrian) in a 10 mile radius !

Victor

colm_mcm wrote: »

I'm not certain these are induction loops. they're always within a few metres either side of overhead signs (the ones I've seen anyway)

The may be positioned near signs so that the electrical system (power and cable trenches) can be shared.

Signs are often near junctions, which is where they will want to count anyway.

rebel.ranter

Have a look at this video. It explains their function and how to trigger them .


http://www.metacafe.com/watch/828731/trigger_green_traffic_lights/

ian_m

rebel.ranter wrote: »

Have a look at this video. It explains their function and how to trigger them .


http://www.metacafe.com/watch/828731/trigger_green_traffic_lights/

nice