Do gantry speed cameras look for big speed changes?

[vsonix]

As the title of the thread -I was driving on the M25 a couple of weeks ago, I was in lane 2 passing trucks in lane one. I observed two cars overtake me in lane three, I would estimate doing between 100-120mph. I won't say they were racing but it did look like they were 'together' if you know what I mean, although they had a few car lengths between them.
Anyway the first car passed the gantry and there was no flash.

However as the second car approached the gantry, a third car pulled into lane three up ahead, causing car number two to brake hard and scrub off a fair amount of speed. So car number two passed the gantry cameras quite a bit slower than car one, however they then flashed a double-flash so I assume car number two was 'caught' but car number one passed through undetected.

The implication was to me that car number one passed through because it was travelling in a safer fashion but the equipment picked up car 2's sudden speed change as being dangerous and therefore pinged it. Is this actually a thing? It seems like quite a good idea if so - pick up cars that behave erratically/dangerously rather than just fast.

[Pdelamare]

Gantry cameras no longer used. Look for the HADECS cameras on the left upright instead.

[vsonix]

OK... so do HADECS do this or was I witnessing something totally different?

[mgtony]

First car was probably obscured by the lorries on the inside lane!

[cmaguire]

Or the flashing you saw was car 2 flashing headlights at the car that pulled out in front of it.

[vsonix]

cmaguire said:

Or the flashing you saw was car 2 flashing headlights at the car that pulled out in front of it.

Nope, it was definitely a camera flash, it came from overhead and they're very distinctive with the double-flash plus it lit up the rear of speeding car #2 and the lane was empty behind it.

Edited by vsonix on Sunday 21st January 16:21

[The Rookie]

Pdelamare said:

Gantry cameras no longer used. Look for the HADECS cameras on the left upright instead.

Yes they are, it’s an either/or with the new Hadecs3 but the existing Hadecs2 are most certainly still being used.

[Somewhatfoolish]

The Rookie said:

Pdelamare said:

Gantry cameras no longer used. Look for the HADECS cameras on the left upright instead.

Yes they are, it’s an either/or with the new Hadecs3 but the existing Hadecs2 are most certainly still being used.

That's not what I was told by the Highways Agency, in writing. If the Camera isn't high viz and it's on a motorway it isn't being used (for enforcement anyway).

[Somewhatfoolish]

Anonymised correspondence fwiw:

Me said:

Hi,



Are any of the original HADECS (or HADECS 2 if they existed?) on the M25 in operation still or is it just the HADECS 3 in operation now?



Cheers!

HA Guy said:

Dear Mr Foolish,



Thank you for your enquiry to CCC recorded below which has been forwarded to me.



The M25 speed enforcement system has been upgraded from HADECS2 & 2.5 to HADECS3 which have yellow casings and are mounted on the side of gantries and MS4s.

A Ministerial directive required that all working speed cameras would be yellow by October 2016.



Regards

HA Guy | SE Regional Enforcement Coordinator | ODSE Operations & Stewardship
Highways England | Bridge House | 1 Walnut Tree Close | Guildford | GU1 4LZ

Web: http://www.highways.gov.uk

Email address: [e-mail]

Me said:

Thanks HA, does that apply to all motorways then, e.g. M1?

HA Guy said:

Somewhat,



Yes.



Regards

HA Guy | SE Regional Enforcement Coordinator | ODSE Operations & Stewardship
Highways England | Bridge House | 1 Walnut Tree Close | Guildford | GU1 4LZ

Web: http://www.highways.gov.uk

Email address: [e-mail]

[cmaguire]

I so want to trust them on that.

[Landshark]

As someone has said already it may have been masked by and HGV, or with HADECS 3 the further to the right you are (lane 4/5) the further down the motorway you are before the double flash compared to the old gantry cameras.

[ghe13rte]

The Rookie said:

Pdelamare said:

Gantry cameras no longer used. Look for the HADECS cameras on the left upright instead.

Yes they are, it’s an either/or with the new Hadecs3 but the existing Hadecs2 are most certainly still being used.

To be fair you have no way of knowing that and most certainly do not know that.

[FurtiveFreddy]

OP, please tell us exactly where on the M25 this happened. Link to Google Streetview would be useful.

[vsonix]

I don't remember exactly - this happened before Christmas and I had basically forgotten about it until it came up in conversation a few days ago. I was heading from the South West towards East Sussex and I wouldn't normally have been using the M25 except I got re-routed that way because of congestion. So it was somewhere between where the M3 would meet the M25 and where I then left to continue to East Sussex, I think I left the M25 near Sevenoaks?

[FurtiveFreddy]

vsonix said:

I don't remember exactly - this happened before Christmas and I had basically forgotten about it until it came up in conversation a few days ago. I was heading from the South West towards East Sussex and I wouldn't normally have been using the M25 except I got re-routed that way because of congestion. So it was somewhere between where the M3 would meet the M25 and where I then left to continue to East Sussex, I think I left the M25 near Sevenoaks?

Well there are a few active cameras on the M25 between the M3 and A21, all are HADECS3 type with the yellow box by the side of the gantry, so it's possible you saw the flashes for one of the cars but the other was shielded by one of the trucks in L1 as someone has suggested. We'll never know.

All the cameras in that section are set at quite a high trigger speed if there isn't a variable limit in place, so if either car went past it at close to or over 100 and the radar had a clear view, they would have been flashed.

These cameras won't be used to enforce a big speed change. If they were, there'd be plenty of people doing being ticketed for suddenly jumping on the brakes when they realise at the last minute they've just gone past a camera!

Edited by FurtiveFreddy on Monday 22 January 16:26

[vsonix]

FurtiveFreddy said:

These cameras won't be used to enforce a big speed change. If they were, there'd be plenty of people doing being ticketed for suddenly jumping on the brakes when they realise at the last minute they've just gone past a camera!

In some ways that's quite a good thing! Nothing annoys me more than people suddenly slamming on the brakes when the way in front is clear.
But the way I had envisioned it might work would be more subtle than that. Drop smoothly from 87-70 - no flash. Suddenly go from 120-70 or slower = flash. Pass through smoothly at 100, no flash.
The idea being that if you have to stand on the brakes from a high speed you are probably driving too fast for the conditions and narrowly avoided a shunt. Therefore you were dangerous, therefore it should be recorded.

Hey guys I think I've invented a new kind of safety camera... [/runs off to patent office]

[superlightr]

vsonix said:

FurtiveFreddy said:

These cameras won't be used to enforce a big speed change. If they were, there'd be plenty of people doing being ticketed for suddenly jumping on the brakes when they realise at the last minute they've just gone past a camera!

In some ways that's quite a good thing! Nothing annoys me more than people suddenly slamming on the brakes when the way in front is clear.
But the way I had envisioned it might work would be more subtle than that. Drop smoothly from 87-70 - no flash. Suddenly go from 120-70 or slower = flash. Pass through smoothly at 100, no flash.
The idea being that if you have to stand on the brakes from a high speed you are probably driving too fast for the conditions and narrowly avoided a shunt. Therefore you were dangerous, therefore it should be recorded.

Hey guys I think I've invented a new kind of safety camera... [/runs off to patent office]

cameras don't record an event of "dangerous"

They just record a speed between 2 distances and known time,

[FurtiveFreddy]

vsonix said:

Drop smoothly from 87-70 - no flash. Suddenly go from 120-70 or slower = flash. Pass through smoothly at 100, no flash.
The idea being that if you have to stand on the brakes from a high speed you are probably driving too fast for the conditions and narrowly avoided a shunt. Therefore you were dangerous, therefore it should be recorded.

What you're describing here is the little used driving technique called "looking and planning ahead" which 99% of drivers seem unable to even comprehend, so punishing them probably wouldn't have much of an effect.

[mandos_01]

If you got off at Sevenoaks, I assume it would have been between J6-5 on the anticlockwise stretch of the M25. A couple of people I know have been flashed for 100mph+ there, and I was flashed doing 61mph when the gantries were showing 50mph

Probably one of the few stretches of the Southern stretch of the M25 where I've actually seen/heard of actual enforcement