M25 new Heathrow section - Gantry Gatso's

[leozwalf]

My dad drove around the 'new' section of the M25 where they have the variable speed limits yesterday. He tells me he saw several gantry cameras flash during the course of the journey (not at him, luckily).

I was wondering if these cameras are actually active. Sure, they flash but is there any film (or are they digital and just hooked up to a network?) in them? 4 cameras (at least) per gantry (one per lane) and 1000's of cars per day... that's a hell of a lot of pictures, especially if the limit is low at the time.

I know other sections of the M25 have had cameras in the gantrys and rulers on the ground for quite a while but have never seen one flash or heard of anybody getting caught by one.

Any info would be appreciated

Thanks,
Leo

[Plotloss]

The cameras definately work but only at the speed they are calibrated for.

So lets say there are two gantries, one has a camera calibrated to activate at 40mph one at 50mph

The signs on both are showing 50mph

Its only the 50mph calibrated camera that will flash if you pass at more than 50mph

They dont, as is often suggested, have a variable trigger point, they go off when they are activated at a speed to which they are calibrated to.

[JonRB]

Plotloss said:

They dont, as is often suggested, have a variable trigger point, they go off when they are activated at a speed to which they are calibrated to.

Sorry, which system are we talking about? Are we talking about my mid-90's film-based system or a new one?

[Plotloss]

Nah, the Gatsos, the ones that you worked on.

I thought it was the case that the trigger point in the camera didnt move...

Or if it did it wouldnt stand up due to lack of calibration at that speed.

[JonRB]

Plotloss said:

Nah, the Gatsos, the ones that you worked on. I thought it was the case that the trigger point in the camera didnt move... Or if it did it wouldnt stand up due to lack of calibration at that speed.

You must have seen me write this a hundred times, Matt!
They are variable but have discrete values - RX (lane closed), 20, 30, 40, 50, 60 and NSL. Each has a used-defined threshold, so what you really have are 7 discrete speed limits whose selection is dependent on what is being shown on the gantry.

The system is calibrated for any integer speed between 0 and 130-odd (I forget the precise figure).

>> Edited by JonRB on Wednesday 11th January 13:33

[Plotloss]

[redacted]

[JonRB]

Plotloss said:

Bloody Carzee, he's had me risking my licence on numerous occasions on that stretch in that case!

Yeah, but he always was a bit of an evil bastard though.

[leozwalf]

Thanks for the replies fellas

Any idea if the cameras are actually active?

[hanse cronje]

came back that way from newhaven, the detector picked them up and scores of cars went whizzing past never saw them flash once

[Gren]

I drive that section twice a day. There are no cameras installed yet.

Every day I look for the boxes - the holes are in the gantries ready to accept them but there is nothing filling them. Like everyone else I've an interest is spotting them the moment they're installed.

Are you sure they weren't either side of the new stretch J10-12 and 15-16?

[7db]

Do they work properly if you are straddling the lanes?