Engineer beats traffic lights ...

[invalid]

Of course you can you stupid sod, dopplers are on the poles not burried.

Its been done.

[whisky-dave]

And if they were then they wouldn't use them for traffic control or counting via doppler shift that is the point that you seem to be missing, differnt types of sensors for detecting and recording various aspects of road usage are used.

Yes I known but I'm not sure if they use such a thing on motorways or B roads. I'd see little point in puttign a camera under tarmac.

[Roger Hayter]

Apparently at the last world athletics thing they put cameras in the starting blocks, for a dynamic view of the runner's crotch as they started; not entirely surprisingly, some of the athletes objected to their use.

[Terry Casey]

Wasn't there a plan a few years ago to install both doppler sensors and cameras into cats eyes to use them as covert speed cameras?

[Terry Casey]

Only when they are first installed, surely?

When the road is resurfaced the induction loops can be (re) fitted before the final layer(s) is/are laid, so no diamonds.

No diamonds means no cuts left to help new potholes form.

[Andy Burns]

Actually, I was specifically thinking of a major junction local to here, where last winter the tarmac did break up really badly where the sensors were leading up to the traffic lights ... after it was re-surfaced they used a big circular saw to re-cut slots for new sensor loops ... give it a few years ...

[Steve Walker]

That was rather the point! the amber, amber/red and time between red coming on in one direction and amber/red coming on in the other are all related to allowing for approaching vehicles to either stop in time or clear the junction in time, so they are determined by the road layout and speed and need to remain fixed.

The green times in each direction dictate how many vehicles can get through each way during each cycle and conversely, how long the red phases are and so how long vehicles must wait. These times can be freely adjusted to maximise flow or prioritise one of the routes.

SteveW

[whisky-dave]

it wouldn't surprise me if some idiot came up with that bright idea, then someone might have told them how much it'd cost with powering the devices by digging up the road and installing cables under the tarmac.

[whisky-dave]

But you won't see them that is the point, why would they leave them uncovered,

traffic would cause to much damage.

that is the old technology.

yes I know, that's what I've been saying. You wouldnlt put a doppler sensor under teh road to count traffic.

That is why I never mentioned them regarding traffic lights, but it does show that having camera at road level is possible but not much use for counting or measuring speeds.

Yes I know that is why I said in the future.

[whisky-dave]

Yes that is pretyy much what I said, but I don't think the amber light changes it's time peroid.

[Terry Casey]

A few years ago, when a secction of the A12 was resurfaced - I think between Brentwood and Chelmsford - a new type of cats eye was fitted. Unlike conventional cats eyes, these had solar cells which charged batteries during the day and light sensors which detected headlights and switched on white LEDs after dark.

I used to do a lot of night work at the time and they were superb. There were a couple of oddities, though. One was seeing the cats eyes still illuminated in the rear view mirror although I was the only car on the road and the other was catching sight of the door mirror as they then appeared as a series of dashes as the LEDs were pulsed.

So, perhaps the 'idiot' that came up with that bright idea also included wifi for communication purposes?

[whisky-dave]

How does knowing what has been used to fill in the cut line help ? How is know it's tarmac tell you what is under it ?

So youre saying it doesn't cover it or it does, make up your mind.

So what does the cover do ?

So ?

I know but dopler is really for measuring speed rather than counting.

But all sensors require power of some sort.

But not all sensors are on poles, that is the point.

I suspect the future will use the signals from driverless cars. The future might mean that the car it;self might use wireless charging technolocgy to briefly charge a device under the road surface so no line cut into the road will be required. A similar thing has been done for years with dog and cat tags and security devices such as expensive items in supermarkets. But this is all near-field tech, far field tech will improve in the furture.

[whisky-dave]

yes I remmebr them a bit expensive but perhaps long term they would pay for themselves but remmebr even recharable battoiers don;t last forever so would need replacing.

You cna buy them yuorself for putting in driveways if you really want to.

I've never tried working out the cost of say putting these in on a particualr motorway. I'm not sure what sort of spacing apart and it would depend on the number of lanes. As you're a driver how much do you think it's cost for say replacing those on the M25 with the LED ones just a guestimate would do.

I can see the advantage but there's also a cost involved. I don't think you'd need to replace the standard cats eye like you would the LEDs ones.

I heard once that there are over 500 million cats eyes in the UK. Excluding real cats)

Perhaps, maybe a micro-doppler for recording traffic speeds could also be added. Ideally they'd only come on when a car is approching them.

[whisky-dave]

So yuo can see through tarmac can you, or do you have x-ray eyes.

yes there is, it can be a hydrolic system for detecting a vehicals wheels going over it thus producing a shockwave rathere that it being a cable transmitting signals

Cameras can do that too.

yes I know so why dig up the road ? Why put additional sensors in teh road that need power and wiring if doppler sense can do it all without having to dig up the road.

No they aren't and that is why they still dig up roads.

yes I know which is why when I say the future I'm not refering to next week which is obviouly in the future too.

They were talking about charging cars from the road, I doubt that will happen.

Yep, so just a fair bit of tweeking to get it to work with cars and signaling.

I know, but not quite good enough.

[Terry Casey]

As you say, I'm a driver, not a road builder!

The spacing on the A12 was no different to the conventional cats eyes they replaced and the cost would have been part of the cost of a major resurfacing programme. It wasn't a separate stand alone excercise.

As for the M25, and interesting question is how long would it take to resurface the entire motorway - with or without LED cats eyes - it won't be in my lifetime, of that I'm sure!