How do average speed cameras work in practice?

TrickyWicky

aliasojo wrote: »

So does this mean the cameras will need to take a picture of every single car that passes them?

Yes. Even if it does not recognise the number plate (ignore previous replies that suggest otherwise) the photo will still be stored and manually looked at. As long as they have the time the camera took the photo and a clear shot of the number plate thats all they need.

I've worked briefly with ANPR and photos of cars with plates that could not be read are flagged to be reviewed manually. That was just for car parking (the industry I was in at the time), imagine how much smarter law enforcement authorities are.

aliasojo wrote: »

What happens if there is a cluster of cars/lorries passing at once on a dual carriageway? Will the cameras be able to pick up every number plate regardless?

Typically the cameras are up on the gantry with one per lane however one camera can also easily monitor two lanes.

Even if it can't pick up the plate for some reason, as long as they have the photo, it can be manually reviewed and the plate number put into the system manually. As long as they have the photo to prove the car was there thats all they need.

westwood68 wrote: »

When they recognise a number plate the computer stores the image at that point along with the recorded time.

Actually it depends on the setup. Some systems will calculate the plate number in real time, others will just take photos triggered by loops in the road and then transfer the photo to a powerful server for processing later. As long as they have the file's creation date/time thats all they need (and most photos are timestamped anyway).

westwood68 wrote: »

If the system don't recognise a number plate, nothing is stored or recorded.

You're talking an urban myth I'm afraid. If it doesn't recognise the plate number it simply flags it up for the operators attention where they can review the plate manually and put it into the system.

westwood68 wrote: »

Hence why bikes are immune to the system as long as the cameras are pointing at the front of the vehicle.

If anyone is interested in seeing basic ANPR at work, you can download a demo program from DTK software:
http://www.dtksoft.com/dtkanpr.php

You'll see it has several 'methods' for recognising number plates - some better than others but it can pick out two plate numbers at a time from some of the sample photos provided (which are installed in the installation directory).

OddballJamie

WTFH wrote: »

Yes, that's mostly because it's dangerous for her and other road users - a slab of snow coming off the roof of the car in front of you will block your windscreen and may well cause you to crash.

I'm pretty certain everyone with common-sense realises the reason why. But thank you for explaining that.

WTFH

OddballJamie wrote: »

I'm pretty certain everyone with common-sense realises the reason why. But thank you for explaining that.

You're welcome

If I could guarantee that everyone had common sense, I'd have said nothing, but I'm sure if I search on here, I'll find a thread about how the police have nothing better to do than to ask people to clear snow off their cars.

WTFH

Bingo:
http://forums.moneysavingexpert.com/showpost.php?p=28450489&postcount=8
http://forums.moneysavingexpert.com/showpost.php?p=28457695&postcount=18


A rather amusing/scary thread.

OddballJamie

WTFH wrote: »

You're welcome

If I could guarantee that everyone had common sense, I'd have said nothing, but I'm sure if I search on here, I'll find a thread about how the police have nothing better to do than to ask people to clear snow off their cars.

Just to add, double the fun when the driver brakes hard and coats their own screen in snow.

Aretnap

wba31 wrote: »

which roads??

A9

Some extra words to make my message long enough to post

neilmcl

Moto2 wrote: »

Also, you never know which ones are being used
In a, say, 5 camera/ANPR section, No:1 may be used in conjunction with No:4 or they may use 4 and 5, or all of them or even none of them.

Is this actually true? I'm aware that they operate in pairs but I was under the impression they were consecutive pairs. Where's the evidence that they do as you say?

TrickyWicky

WTFH wrote: »

Bingo:
http://forums.moneysavingexpert.com/showpost.php?p=28450489&postcount=8
http://forums.moneysavingexpert.com/showpost.php?p=28457695&postcount=18


A rather amusing/scary thread.

I don't know whats worse, the two posters attitude or the number of people who thanked them for posting!

Ultrasonic

Cornucopia wrote: »

It seems likely that trigger speeds for offences are set slightly higher with average speed systems compared to the traditional speed cameras to allow for inaccuracies in measuring what can be a long piece of road between the sample points.

I'd actually have thought that average speed checks would be far more accurate than traditional speed cameras (since the likely timing or distance errors would be a very small percentage of the total distance and time). The speeds at which the system is set to issue fines is a different matter, but it would make sense to me if they were lower. If they are or not I have no idea though!

spacey2012

Our number plate digits are much larger than is required by law, unless it has changed, when you see a bare legal plate on a motorcycle, they would need good resolution to read that.