Average Speed Cameras

[Bazile]

As i understand it average speed cameras work by recording the time taken to travel a set distance between two cameras .
There can be multiple sets of cameras over a stretch of road where it operates .

If the speed limit of the road is 30mph and your speed between these multiple sets of cameras is always over 30 , eg 31 , your average speed will calculate to be over above 30mph - yes ?

Therefore you will need to travel for the entire length of road at a speed of 30mph or lower , for the average to calculate at 30 or lower ?

[Ellipsis]

> Therefore you will need to travel for the entire length of road at a speed of 30mph or lower , for the average to calculate at 30 or lower ?

I believe the way they work is to measure the time it takes you to get from A to B. Since they know the distance from A to B, speed = distance / time. This means that you could go above 30 for some of the way, as long as your average for the whole distance was below 30.

[furrypusscat]

There may be some areas due to traffic congestion and time of day that you may well be doing less than 30mph so will average the whole journey between the first camera and the last therefore allowing a small percentage to be over the limit. I think this is a fairer system than static cameras where people speed after they have gone beyond the camera and slow down before the next. Answer is of course, Don't speed.

[Old_Geezer]

No, you do 100 mph for most of the stretch then stop for a flask of tea and a bickie for 10 minutes before restarting and passing the next.

[Gizmonster]

//// Therefore you will need to travel for the entire length of road at a speed of 30mph or lower , for the average to calculate at 30 or lower ? /////

.... incorrect.

Let's assume the following:

You travel from camera 1 to camera 2 and they're 5 miles apart.

If you travel at a constant 30mph, it'll take you 10 minutes to get from camera 1 to camera 2.

Now if you decide to travel at 60 mph, it'll only take you 5 minutes and if you pass camera 2, it'll register that you only took 5 minutes to travel 5 miles, so your average speed will be clocked at 60mph.
If, however, you stop just before camera 2 and wait 5 minutes before you decide to pass camera 2, the camera clocks you as taking 10 minutes to travel 5 miles and your average speed will be calculated as 30mph.

you can do the same with other speeds:

90mph - takes 3 minutes 20 seconds to travel 5 miles. Pull in, wait 6 minutes 40 seconds before passing camera 2 and average speed will be calculated as 30mph.

[ToraToraTora]

you see this on tolls in France. Bikers who think they have gone to fast will stop prior to the reader so their average is legal. As OG says you can do 100mph and stop before the detection point and fool it. Say there was a 10 mile stretch with 30 limit you could do 40 for 5 miles and 20 for 5 miles, for example.

[CrapAtCryptics]

Stick the cruise control on 29mph problem solved

[Gizmonster]

///// Say there was a 10 mile stretch with 30 limit you could do 40 for 5 miles and 20 for 5 miles, for example. /////

An increase of 10mph for half the distance, will not be properly balanced by a reduction of 10mph for the remaining distance - it's all about incremental increase/decrease, rather than unit increase .... or something like that lol :P

If you travel half the distance for 40mph, you only need a speed of 24mph for the remaining distance:

40mph for 5 miles takes 7.5 minutes ... this leaves 12.5 minutes to cover the remaining 5 miles = 24mph.

[Bazile]

They have introduced ASC in various locations in my area .

The length of the roads that they are operating over is around a mile .

Now if i'm driving along the stretch of road , i'm not going to be constantly checking and adjusting my mph for set distances or stopping and moving off again , etc which would be difficult to do in any case .

So isn't it just easier to keep below the speed limit for the entire distance of the zone?

[Zacs-Master]

Erm.....yes. That's what they're there for.

[Gizmonster]

//// So isn't it just easier to keep below the speed limit for the entire distance of the zone ////

That is the whole point of cameras - to stop people speeding .... but, if you're travelling along a stretch of road with average speed cameras and you "accidentally" exceed the speed limit - it is possible to avoid being caught by stopping for a short period of time.

[chiaroscuro]

Is it an offence to use a hand held calculator whilst driving?

[DTCwordfan]

climb up the 2nd camera tower and spray black paint over it....given the time involved in doing this, you will probably be back under 30 mph anyway.

[Quoi]

...and they have a tolerance the same as standard speed cameras so the last paragraph of your question is not true.
I was told by someone who installs them its 8mph about the limit in a 50mph zone but dont go testing it unless you are sure (i have though)

[New Judge]

The ACPO guidance for prosecuting speeding offences is that enforcement should not normally begin until (Limit + 10% + 2mph). So 35mph in a 30 zone, 46 in a 40 etc. This is to prevent large numbers of frivolous challenges to the accracy of the equipment used. This guidance applies whether the measurement is taken by automatic device or is measured by a police officer.

However, many motorists mistakenly believe that this higher figure is therefore the new limit. They are mistaken as enforcement can occasionally begin at lower speeds and any excess over the limit can be prosecuted. I came across a case a few weeks back where a driver was accused of doing 44mph in a 30mph limit. He argued that the 30mph signs were obscured at the beginning of the new limit where it had reduced from 40mph to 30mph. The court accepted his argument but convicted him anyway because he had exceeded the limit that he believed applied.

[douglas9401]

On the A9 from Dunblane to Inverness the entire length is covered by these cameras. There's also an increased limit of 50mph for HGVs on single carriageway sections..
I guess the cameras can't differentiate between said trucks and cars which have a limit of 60mph on the same road as I'm often overtaken on the longer straight sections by artics when I'm doing 53mph in my wee truck so they're obviously doing considerably more.
That suggests that either the cameras are 'dumb' or there's a considerable leeway given.