OT: Anyone been had by the digital cameras on the M1 road works (jct 8-10)?

The message from Art Deco contains these words:

Wish I could have averaged 40mph there on Wednesday morning. I was lucky to get an average of about 15 through there.

Someone told me the way it works is as follows: if one camera "sees" you going at over 40 mph, the next one is set to clock you and check your average speed between the two. Does that sound right or do all the cameras check all the average speeds of all the vehicles all the time?

The message from Art Deco contains these words:

There's no particular reason why it shouldn't measure everyone - it's not like ANPR is hard to do these days and the amount of data even on a busy motorway would hardly tax a modern desktop PC.

They check the average speed of every car, however each SPECs camera can only do one lane, so on a three lane or more road, it is possible to pass them all without your car even being noticed.

How does that work?

Three lanes, two cameras that can only do one lane each. You do the maths.

It seems that there are two cameras at each camera point, focused on the two outer lanes.

Two cameras with wide angle views to give 50% redundancy in case a truck blocks the view of one??

AJH

I don't know if you've driven on that particular stretch of M1 recently, but the cameras are positioned on specially constructed overhead gantries, rather than at the side of the road.

Even so, the cameras view the carriageways from an angle, so you may be right.

And I should have said the two 'faster' lanes rather than the two outer lanes.

Yes, I do a service contract there during the winter months so was going a couple of times a month. It struck me the gantry carried two cameras and shared an infra red light in the middle, as they appeared the same size and shape as the blue cameras originally used for traffic monitoring which read 3 lanes I guessed one was for corroboration or redundancy. I don't think the hardware or software would have much trouble recognising, storing and calculating average speed of a traffic stream nowadays.

Mind whilst people seldom speed on this stretch there is always someone in a ford pottering along at an indicated 40, true 35, that keeps the average in the section well down.

AJH

Would you risk going at an indicated 45 (true who knows what?) and risk 3 points plus 60 quid?

I tend to travel in the inside lane with the trucks, their speedometers are a lot more accurate than old car ones and they are very concerned about their licenses. Also the GPS tends to be fairly accurate.

AJH

You haven't been looking closely enough. The little yellow cameras have an infra red source each side of the lens.

The first time I went though this one there were lots of people collecting fines by doing 60 mph between the cameras and only slowing down for the cameras. Maybe they could sue thier schools for not teaching them what "average" means!

Oddly when the same system was up near J21 everyone got the hang of it straight off.

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So do I.

Conor claims they're all speed-limited to 56mph or something these days, at least on level ground. The empirical evidence seems to suggest otherwise.

At least on level surfaces...

The message from Art Deco contains these words:

They mostly seem to be - though there's the odd one or two that stick out like a sore thumb. The ones that drive me potty are the ones that overtake another truck when they're both governed to 56mph - the tolerance is pretty tight so it can take a couple of minutes to finish passing. On a two-lane motorway that's fairly irritating for everyone else.

Give or take. I've driven some as low as 52 and others as high as 58.

Meaning?

I don't think the speed limiter is necessarily linked to the tachometer, the speedo is part of the tachometer and these have to be in calibration.

In fact I think DAF trucks are all speed limited at a bit less that

This is all a bit of a red herring when it comes to maintaining 40mph on the speed limited stretch, I think the HGVs maintain this speed nearly spot on if their way is clear.

AJH

Fairy Nuff, I'll look again next time I go by.

AJH

How easy is it to override the speed governor mechanically, I wonder.

Meaning if I'm doing just under 60, quite a few of them still manage to overtake me.