(16 Posts)
Kitkat05 Thu 22-Jul-21 17:04:30

Hi all,

Today was the first time I drove on motorway. M1 and M25.

Google maps showed 70 but I was going at 60.. lots of variable speed cameras.. some parts speed limit changed to 40, 50 then 60 then no sign.

Noticed variable speed cameras at points where speed limit changed. I got a bit confused..tried to stick to the limits. Everyone else was over taking going really fast.

How do variable speed cameras work? Just a bit worried as speeds kept changing, my first time.. and would like to know how they work.

Did google but think im too tired to understand.

OP’s posts: |
name6785 Thu 22-Jul-21 17:22:16

Ignore sat nav speeds and just do what the motorway tells you. Smart motorways adjust the speed limit depending on the traffic ahead, it is clearly listed and often lots of cameras, ignore what anyone else is doing that's their risk, stick left unless you're overtaking and away you go (although be careful if going into the hard shoulder as they are often for an upcoming exit).

name6785 Thu 22-Jul-21 17:24:17

And I don't think they're the variable ones unless in road works, smart motorway ones are usually just attached to the overhead things (not sure what called sorry) so if you go over 60 when it's set to 60, you will be caught (not sure on how much "over" you can go). I've seen a lot of flashing from those cameras!

name6785 Thu 22-Jul-21 17:24:32

Not for me I hasten to add!

nothingcanhurtmewithmyeyesshut Thu 22-Jul-21 17:30:08

They scan number plates and time how long it takes you to get from camera A to camera B. If it takes you, say, 50 seconds and this could not be done without breaking the speed limit, you get a fine.

nothingcanhurtmewithmyeyesshut Thu 22-Jul-21 17:30:56

And Jesus christ, the M25 as your first motorway? Talk about a baptism of fire.

pastafeend Thu 22-Jul-21 17:31:19

Are you actually asking about how the speed cameras work or the variable speed limit?

The speed limit varies according to traffic and you adjust your speed accordingly just like you would in an urban road with a speed limit change.

If you do this the speed cameras themselves are irrelevant to you.


AlwaysLatte Thu 22-Jul-21 17:31:37

M25 is not so bad. I regularly get free parking there!

name6785 Thu 22-Jul-21 17:32:08

@nothingcanhurtmewithmyeyesshut to be fair it doesn't move much and you're rarely able to go over 60 so probably a good shout actually ha!

BadgeronaMoped Thu 22-Jul-21 17:35:14

Agreed, ignore the satnav's speed instructions and read the speed signs as you drive. Variable speed limit means exactly that, it'll change up and down. Average speed limit generally gives you a number such as 50mph and checks at various points along the route.

Also, many of the cameras you see will be highways agency traffic monitoring cameras.

Tommika Thu 22-Jul-21 17:37:02

Ignore other drivers, obey the limit showing.

But if a limit sign changes as you’re approaching just drop speed and don’t slam the brakes. There is a time delay (if I think 10 seconds) between the change before an associated speed camera enforces the change
(That is when an individual sign switches from 70 to 60 etc. Not when you come from a 70 stretch to a 60 stretch)

Many people ignore speed cameras on the assumption that they are off, but you never know

There is a factor that the speed showed by your car over accounts for your actual speed, and there has historically been a 10% allowance by speed cameras before prosecution
Combine those and you can often ‘get away’ with speeding. But the 10% allowance doesn’t always apply as the machines are accurate and a cars speedometer may be right

On the motorway you will commonly get average speed cameras at roadworks etc which ensure you are doing no more than displayed between each pair of cameras - it’s no good slowing to pass the camera
And the variable speed limits will probably have a camera behind each display panel

You drive as you feel safe, and let the others shoot off ahead

Drive consistently and you get there steadily
Speed and you typically catch up with the delays ahead
That’s the whole point of variable limits to space out congestion, but when people floor it they just generate waves of congestion

Kitkat05 Thu 22-Jul-21 18:01:06

Thank you @name6785 @pastafeend @nothingcanhurtmewithmyeyesshut @Tommika @BadgeronaMoped @AlwaysLatte that really helped.

@nothingcanhurtmewithmyeyesshut tomorrow will be 2 years since I passed my driving. I work local so have never needed to use any motorways.

OP’s posts: |
nothingcanhurtmewithmyeyesshut Thu 22-Jul-21 18:43:16

I did them in driving lessons just, was allowed about a week before my test, which I'm glad of as it's the easiest route to the next town where my gym is and my therapist is in London so need to get to him too.

I think it ought to be standard in driving lessons now as people travel more than they used to.

BertieBotts Thu 22-Jul-21 18:48:34

Those speed limit add ons for Google can be out of date, so only ever use it as a rough idea, if in doubt assume whichever is lower.

girlmom21 Thu 22-Jul-21 18:49:20

Average speed cameras will only capture you in areas with consistent speeds, like road works.

Any other speed cameras on a smart motorway will only catch you if you're exceeding the speed overhead.

girlmom21 Thu 22-Jul-21 18:49:36


M25 is not so bad. I regularly get free parking there!


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