# Average speed cameras

How do they work? I was coming back from somewhere today tired, it was a four lane dual carriageway and weirdly despite having no obvious reason as to why it shouldn’t be a 70, it was a 50, and as I was about to pass a speed camera or did (the yellow one) I saw 61 on the dashboard. I then drove at about 42mph to the next one. Would that average out my speed fo ensure that the 61mph average would be reduced?
if you go over the limit by 6 or more mph, this will flag it up to the Police who then send you a letter in the post.

have you considered a speed meter on your car?
Original post by JVM2020
if you go over the limit by 6 or more mph, this will flag it up to the Police who then send you a letter in the post.

have you considered a speed meter on your car?

You’re wrong , there’s a general 10%+2mph rule nothing in law about it being 6mph.

Also eve then that applied to normal speed cameras not average ones
According to the AA
"Average speed cameras work by recording your speed at two different points. They don't capture your speed in a single flash. Instead, they'll monitor your speed over a length of road. This is so people don't slow down just before they see a camera and then speed up again afterwards"
Original post by Anonymous
How do they work?

They don't look at your speed at all. They divide the distance between the two cameras by the time between you showing up on them. If you drove almost the entire distance between them at 42mph then your average speed will only be very slightly over 42mph.
Original post by skylark2
They don't look at your speed at all. They divide the distance between the two cameras by the time between you showing up on them. If you drove almost the entire distance between them at 42mph then your average speed will only be very slightly over 42mph.

So I don’t know if that means I’ll get fined or not as there were like three cameras , between one set I defo did 42 but on the other camera i recall about to pass it at 61
Original post by Anonymous
You’re wrong , there’s a general 10%+2mph rule

There's guidance about "10%+2mph" -- but it's guidance that the police are free to accept or ignore.

No idea whether that guidance applies to average speed cameras, or just to fixed/mobile cameras that do an instantaneous speed reading.

@IWMTom -- any thoughts?
Original post by martin7
There's guidance about "10%+2mph" -- but it's guidance that the police are free to accept or ignore.

No idea whether that guidance applies to average speed cameras, or just to fixed/mobile cameras that do an instantaneous speed reading.

@IWMTom -- any thoughts?

IIRC average soeee cameras don’t check speed only time etc

I spoke on a forum to a guy who installed the cameras on that stretch of road. Only one set of them actually works. So I might be lucky
Original post by Anonymous
You’re wrong , there’s a general 10%+2mph rule nothing in law about it being 6mph.

Also eve then that applied to normal speed cameras not average ones

my maths needs strengthening
Original post by martin7
There's guidance about "10%+2mph" -- but it's guidance that the police are free to accept or ignore.

No idea whether that guidance applies to average speed cameras, or just to fixed/mobile cameras that do an instantaneous speed reading.

@IWMTom -- any thoughts?

Yeah that's what used to be the ACPO guidance. Less about "inaccuracies" and more about reducing paperwork for small time offenders.

Applied to any speeding offence regardless of detection method.
Original post by IWMTom
Yeah that's what used to be the ACPO guidance. Less about "inaccuracies" and more about reducing paperwork for small time offenders.

Applied to any speeding offence regardless of detection method.

The road in question is the A13. I joined the road near Canary Wharf, and left at the M25. I believe I only lapsed and got up to 61mph on the 50mph section near Thurrock (don't ask me why its 50 and not 70 when its a six lane dual carriageway with no buildings or anything alongside it). Other than that I obeyed the speed limit or went below it. Does the average speed check work like that? Measuring the entire length of your journey on that road rathe than just between two points?
Original post by Anonymous
The road in question is the A13. I joined the road near Canary Wharf, and left at the M25. I believe I only lapsed and got up to 61mph on the 50mph section near Thurrock (don't ask me why its 50 and not 70 when its a six lane dual carriageway with no buildings or anything alongside it). Other than that I obeyed the speed limit or went below it. Does the average speed check work like that? Measuring the entire length of your journey on that road rathe than just between two points?

It measures between two sets of cameras, but you never know which sets of cameras are connected together. That's sort of the point.
Just a quick question does traffic lights affect the average speed cameras. where I live there is a set of traffic light between first camera and second camera.
Original post by Peter38
Just a quick question does traffic lights affect the average speed cameras. where I live there is a set of traffic light between first camera and second camera.

No, they’re unrelated.