Help - Search - Members - Calendar
Full Version: Do Gatsos ever fire when you're traveling at/below the limit?
FightBack Forums > Queries > Technical Discussion of Enforcement Devices
Chris1207
Hi All,

Question as per topic title. Do Gatsos ever fire when you're traveling at/below the limit? If so, what can cause this?

This one, M9 north (J1) under Newbridge Roundabout in Edinburgh, flashed me last night.

I knew it was there, and as I was driving a heavily loaded truck, which was going downhill, I was holding my speed back on the brakes, and keeping a rather close eye on it. Immediately before it, and after thinking WTF and double checking... speedo was indicating exactly 50 (reads over slightly), tacho was reading 77km/h, and GPS on my satnav was indicating 48/49.

It really confused me at the time, and I was doubting myself that it's a 50 limit, even though I know it is. Also, shouldn't the camera be set to only flash 57mph+, per guidelines? Truck is limited to 56 mph (actually 55, 89kmh) - the retarder generally does a good job of keeping you at the limiter, though it will overspeed on long/steep downhills when loaded, hence why I was holding it back on the brakes. But that'd equate to a minimum of 92kmh. Simply wasn't happening.

Assume that Lothian & Borders SCP will do the secondary checks before sending anything out, and they wouldn't prosecute under 57mph anyway, would they ? Also, I noticed that it didn't flash as I passed it, it flashed after I was quite a bit along the lines on the road.

I know, I'll just need to wait and see if anything comes of it... but it's bothering me - first time I've ever been flashed rolleyes.gif

I've heard that Gatsos can give false readings from large reflective surfaces? I was driving a large metallic (very shiny!) tanker, which is flat at the back. Might this have thrown it off?
Chris1207
QUOTE (PASTMYBEST @ Wed, 7 Jan 2015 - 12:29) *
if your tacho is out that much should you have been driving the truck


Eh???
PASTMYBEST
sorry was skim reading mistook kph for mph you've got no worries then tacho proves your case
The Rookie
A Gatso housing can contain a dummy unit with basic radar and flash but without the expensive camera, they are often set to flash right on, or even just under, the limit. Was flashed by one on the M6 once when doing 51 in a 50 limit, it was quite literally flashing every vehicle that passed.
mickR
The one near me started doing that. It even started flashing oncoming vehicles. I phone the scp they said yes we know it's got a fault. Never heard anymore but it was not flashing the next day.
StationCat
Gatso's are very old technology and not particularly sophisticated. They can pick up reflections of other vehicles from large vehicles, so it may be that a car behind you was over the threshold and the radar beam was bouncing off the back of your truck and detecting that vehicle.
Rallyman72
Travelling down the M6/M42 back end of last week, traffic at 20mph and solid, limit on gantry 40mph, tanker about 5 or 6 in front of me gets flashed ...
The Rookie
QUOTE (StationCat @ Sun, 11 Jan 2015 - 18:24) *
Gatso's are very old technology and not particularly sophisticated. They can pick up reflections of other vehicles from large vehicles, so it may be that a car behind you was over the threshold and the radar beam was bouncing off the back of your truck and detecting that vehicle.

You think, how would that give a Doppler effect similar to a vehicle going away faster? If anything for that to work the car behind would have to be going slower....
StationCat
Yes, thinking about it, it would have to be something going away from the reflection. However it happens, they do sometimes take odd shots with spurious readings.
Rallyman72
And in the case I witnessed on Thursday it was impossible, we were all doing about 20mph nose to tail yet a variable limit Gatso set at 40mph still went off.
The Rookie
It was impossible and happened? Really?

As it's doppler radar it only needs to see a frequency shift that matches the return from a vehicle travelling over the threshold, stationary lorries have achieved that, so I'm sure one travelling at 20 could.

That said I didn't think Gatso's were used in variable anymore, just HADECS and they do an occasional test flash as I understand it.
Rallyman72
Simon, I was responding to the idea that individual vehicles in the traffic stream were travelling at more than the limit. In this instance it was a nice shiny tanker doing 20mph with a car behind it doing the same speed that got flashed.

OK, so it was a HADECs then.
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2018 Invision Power Services, Inc.