M25 Variable Speed Limits

[RedLCRB0b]

My first post on SPL, please be gentle

Was approaching one of the M25 cameras at the weekend, current speed was 60 (as requested by previous sign). About 20ft away from the next sign and it flickers down to 50, and then almost immediately down to 40. Had to do a fair amount of braking (which didn't really feel very safe) to get to the correct speed. Is there some sort of tolerance for going through these things just after they have changed speeds ?

Cheers
Bob

[JonRB]

RedLCRB0b said:

Is there some sort of tolerance for going through these things just after they have changed speeds ?

Yes. When the limit changes there is a user-defined "grace period" during which the system does not enforce.
From memory the default value was 5 mins, but of course it could be anything the operator wants.

[RedLCRB0b]

Cheers Jon, I wonder what tolerance they use on the M25?

Bob

[JonRB]

RedLCRB0b said:

Cheers Jon, I wonder what tolerance they use on the M25?

Tolerance in what sense? If you mean enforcement speed then each speed limit (Red X, 20, 30, 40, 50, 60, NSL) has a different user-settable tolerance of 0-99mph which is added to the speed to give the speed over which enforcement occurs.

If, however, you're wondering out loud what the grace period is set to on the M25 then I can't help you. I have no idea what the operators are setting it to.

[RedLCRB0b]

JonRB said:

Tolerance in what sense? If you mean enforcement speed then each speed limit (Red X, 20, 30, 40, 50, 60, NSL) has a different user-settable tolerance of 0-99mph which is added to the speed to give the speed over which enforcement occurs.

No not this one, although given the speed I have seen people going through these at I think it is quite a bit more than the posted limit.

JonRB said:

If, however, you're wondering out loud what the grace period is set to on the M25 then I can't help you. I have no idea what the operators are setting it to.

Yep this was the one, and I was wondering out loud

Bob

[mcflurry]

if the scameras have regular film the triggers are set very high or the 800 piccies would be used up very quickly Digitals are a different story though

[JonRB]

The M25 cameras do use film.

On start-up they fire 2 test shots, so that's 498 left.
Every time the speed limit changes they also fire 1 or 2 test shots (I forget which).

And to change the film, an operator has to physically go to the camera enclosure, so for the outside lane that involves crawling along the gantry.

However, when the camera runs out of film it enters "dummy mode" which means it flashes twice to make the motorist thing he's been snapped, although no offence is recorded (obviously - because there's no film left).

[V6GTO]

Used to go out with a female trafpol seargent, she told me how they were set so when I had my bike I used to go under the bridges at 99.9mph! Don't take the p1ss when the limit comes down though, + 10mph max. Martin.