Traffic Lights with sensors

iain_j

rhext wrote:

I've had unpleasant experiences with temporary traffic lights too. There's a road coming out of Buxton called something like 'Long Hill' - no imagination when it comes to road names there! I got forced off the road in a set of temporary lights there once!

I hate these temporary traffc lights on hills. Usually not enough time for a cyclist to get through if they go through near the end of the spell on green. And regardless of the fact there's still a cyclist coming the other way a lot of motorists still drive at you when they get the green.

tiki tourer

when a ferrous object passes over it

Wikipedia:

Aluminium is the most widely used non-ferrous metal.

I think I'm starting to see the problem...

Kieran_Burns

lost_in_thought wrote:

Slightly OT, but beverick's very informative post reminded me of a question I had: you know when sometimes there are those black cables stretched across the road? Usually in pairs? What are they for?

Generally speed sensors

If they are exactly a metre apart then the Police are thinking about a speed trap. This is to see if they will bag enough to make it worth while.

solsurf

I had to wait for over 5 min for a car to arrive behind me going to kendal a couple of weeks ago. The red light refused to change :x there was no way through as the road is narrow with no foot path. It was seriously annoying.

The temp lights have gone now though.

I suppose I am lucky I only have a couple of traffic lights on my 9 mile commute and a level crossing. So most of it is a clear ride through.

Canny Jock

I've often been stuck at the lights turning right over Tower Bridge, heading south. The lane is only for taxis and bikes, fortunately a cab normally turns up without too much delay.

From memory, they've never turned without a taxi being there. I'd love to know a way to trigger them on the bike.

iain_j

solsurf wrote:

I had to wait for over 5 min for a car to arrive behind me going to kendal a couple of weeks ago. The red light refused to change :x there was no way through as the road is narrow with no foot path. It was seriously annoying.

I usually give up after about a minute, or after seeing a whole cycle of green lights around a junction with me still waiting at a red. Depending on where it is or what time of day, it's not always feasible to wait for a car to trigger the lights. Trouble is, it's not always feasible to jump the red light that's just not going to change, like crossing a busy dual carriageway.

Snudge

redvee wrote:

Attica wrote:

There's one like this on my commute - opposite the Hippodrome a Ped Crossing in the Buses and bikes only section, only ever triggered by buses

This the set of lights at the end of Baldwin Street? If the buses coming the other way, away from Broadquay, get the green light then I'll jump the red on my side :oops: If I've got a bus behind me then I'll pull forward well ahead of the white line so that the bus is recognised by the lights. If the lights are red and no buses present then I'll get the Metro out from the bags beside the railings and read it whilst waiting.

Those lights are ridiculous. They control what is a pedestrian crossing and yet (with plenty of room for 2-way traffic) show a green light to traffic going one way (North) and red lights to pedestrians and Southbound traffic which has to legally clear the box junction and may be legally prevented from doing so by a pointless red light further on. Why not change to green both ways when triggered by a vehicle from either direction? Perhaps a pedestrian is half as likely to be killed! And people have been killed around there. I go through on red Southbound when a bus is coming through the other way because I know it's green the other side and there is no reason for me to stop as the only reason for no green is that the sensor hasn't been triggered. This is only done by me because of local knowledge and experience.

I am also interested to know where the junction mentioned in post # 13 (nettles) is.

lost_in_thought

Kieran_Burns wrote:

lost_in_thought wrote:

Slightly OT, but beverick's very informative post reminded me of a question I had: you know when sometimes there are those black cables stretched across the road? Usually in pairs? What are they for?

Generally speed sensors

If they are exactly a metre apart then the Police are thinking about a speed trap. This is to see if they will bag enough to make it worth while.

Ahhhh I see! Thanks for that!

gert_lush

lost_in_thought wrote:

Kieran_Burns wrote:

lost_in_thought wrote:

Slightly OT, but beverick's very informative post reminded me of a question I had: you know when sometimes there are those black cables stretched across the road? Usually in pairs? What are they for?

Generally speed sensors

If they are exactly a metre apart then the Police are thinking about a speed trap. This is to see if they will bag enough to make it worth while.

Ahhhh I see! Thanks for that!

ooh I always thought they where to count traffic or something, every days a school day, cheers

jimmypippa

tiki tourer wrote:

when a ferrous object passes over it

Wikipedia:

Aluminium is the most widely used non-ferrous metal.

I think I'm starting to see the problem...

Not really a problem: (I'm jimbob on badscience.net BTW)



Subject: Holy (not allowed on bikeradar) my friends are muppets help me combat anecdata!

jimbob wrote:

AntibodyBoy wrote:

Some sort of special magnetic aluminium is it? :roll:
Maybe its just your personality that causes the induction; the electrons can't get away fast enough....

Changing EM field induces eddy currents in a conductive material, which then cause magnetic fields.

EDIT:

A quick google search found this PDF

http://www.earth-prints.org/bitstream/2 ... %20version).pdf

http://www.earth-prints.org/bitstream/2 ... %20version

3.6 Three magnets falling
The next exhibit consists of three different vertical tubes where a concentric magnet can fall for gravity
(Fig. 8); the three tubes are respectively made of aluminum, plastic and copper; the magnet falls with
different speeds, going fast when there is a plastic tube, slow for aluminum, and very slow for copper.
All these materials are magnetically negligible (not ferromagnetic), and the different effects are due to the
ability in conducing electricity; the magnet, moving, induces electrical currents opposite to the directions
of the movement; the consequent magnetic field, for the falling magnet, results a sort of “magnetic
friction”. This effect is obviously as strong as conductive is the medium. This is a first view of the
strong connection and interaction between magnetism and electricity.

I was hoping for a video of inductive sorting of aluminium cans, which can "fly" off a conveyor belt when exposed to the changing EM field.

But of course carbon bikes will be a lot less conductive than aluminium ones

abductee

I have the same problem. My steel bike triggers the sensor but my aluminium one does not. I guess I shall have to lay the bike down in the road over the sensor as advised. Should I lay in the road with it? and if so for how long?

beverick

lost_in_thought wrote:

Slightly OT, but beverick's very informative post reminded me of a question I had: you know when sometimes there are those black cables stretched across the road? Usually in pairs? What are they for?

They're temporary traffic counters. They are usually placed along routes or in areas to help build up a traffic flow model.

The cables are in fact rubber tubes and the counter (they used to be mechanical) is triggered by air pressure.

Kieran_Burns wrote:

lost_in_thought wrote:

Slightly OT, but beverick's very informative post reminded me of a question I had: you know when sometimes there are those black cables stretched across the road? Usually in pairs? What are they for?

Generally speed sensors

If they are exactly a metre apart then the Police are thinking about a speed trap. This is to see if they will bag enough to make it worth while.

I'm pretty certain that they are not used for speed averaging anymore - they were notoriously unreliable. The main problem was being able to to record the time taken for a vehicle to move over the sensors. It's easy where vehicles have the same axle configiration and are the same length but given a mixture of vehicles it gets difficult. For example two bendy-buses pass over the sensor will give the same pattern as three wagons.

Most speed sensors are infra-red detectors and are either hand held (or vehicle mounted) or are placed on roadside poles.

Bob

asprilla

gert_lush wrote:

lost_in_thought wrote:

Kieran_Burns wrote:

lost_in_thought wrote:

Slightly OT, but beverick's very informative post reminded me of a question I had: you know when sometimes there are those black cables stretched across the road? Usually in pairs? What are they for?

Generally speed sensors

If they are exactly a metre apart then the Police are thinking about a speed trap. This is to see if they will bag enough to make it worth while.

Ahhhh I see! Thanks for that!

ooh I always thought they where to count traffic or something, every days a school day, cheers

Got a source for that?

Given you don't know the wheel base length of the vehicles or how close together they are you can't possible measure speed with them

AFAIK they are just fo counting traffic volumes.

paul-yokaholnes

is it illegal for temp traffic lights as well? I heard somewhere that you can go through these if the coast is clear... does not sound right to me though.

Mr_Cellophane

First time I cycled to London on a Saturday, I waited ages here for a bus to come along.

http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=london&sll=-34.886213,-58.512669&sspn=0.054917,0.102139&ie=UTF8&hq=&hnear=London,+United+Kingdom&ll=51.511627,-0.006309&spn=0.010416,0.025535&z=15&layer=c&cbll=51.511584,-0.006523&panoid=-FE40h1mCIso7BImhq0hog&cbp=12,251.85,,0,-0.6

When I started commuting I just took my life in my hands and pulled across to the right hand lane.

tiki tourer

As a follow up to this, I have had a reply from the council. They have made some adjustments that should help. In short the message is "aim for the X" - apparently it is the most sensitive part of the pad. Also, the lights are only triggered if you stay still for at least 4 seconds.

The lights did work for me this evening despite a total lack of buses.

Apparently there have been fatal accidents at this crossing (I'm guessing ped hit by motor vehicle). Hence the 4 seconds stop I think.

redvee

tiki tourer wrote:

"aim for the X" - apparently it is the most sensitive part of the pad.

Will try and find that in the dark tomorrow at 7am, maybe I ought to get out with some illuminous paint?