Average speed cameras

[kwicky]

What leeway is given when exceeding the speed limit between 2 overhead cameras?

[sddsddean]

Legally a car speedo must read within 10% of the actual speed (unless they've changed the law!) and a truck and a bus speedo must read within 6kph of the actual speed, so as the car 'leeway' is bigger, I would imagine they have to allow for that. So on a motorway (assuming its in a 40mph roadworks) you could probably average 44mph OK...but don't rely on me in court!!

[THECORBYLOON]

The 10% means the speedo can show a speed 10% higher than the actual speed but must not show lower than the actual speed. This means if the speedo shows 40mph the actual speed could be between 36mph and 40mph.

[ash24]

I was of the opinion that the formula was 10% of the restricted speed PLUS 4 miles per hour.
I also seem to remember a move to rescind the "4 mph" bit but please do not rely on this info either ...

[kempie]

There are two different issues being debated here.

EC Community Directive 75/443(97/39) and ECE Regulation 39 lay down accuracy requirements to be applied at the time of vehicle approval for speedometers. These requirements are that the indicated speed must not be more than 10% of the true speed plus 4 km/h (or 2.4mph), and that the indicated speed must never be less than the true speed.

For the past 7 years the ACPO (Association of Chief Police Officers of England, Wales and Northern Ireland) Guidelines for Speeding Enforcement have recommended, other than in the most exceptional circumstances, the issue of fixed penalty notices and summonses by a Police Officer is likely to be the minimum appropriate enforcement action for speeds based on the formula Speed Limit + 10% + 2 mph. However The Police Service now uses technology that enables it to prove that an offence has been committed as soon as a driver exceeds the relevant speed limit by a very small margin. Motorists will therefore be at risk of prosecution immediately they exceed any legal speed limit.

http://www.acpo.police.uk/asp/policies/Data/sp eed_enforcement_guidelines_web_v7_foi.doc

[kwicky]

I would have thought there is less leeway when tracked over a longer distance as speedos in modern cars, being digital, are more accurate than the older versions whereas Gatso type cameras, being instantaneous, are easily tripped.

[buildersmate]

Gatso types may be instantaneous but they are no less accurate, using a version of the Doppler Effect to calculate the speed of the vehicle. And they use digital technology as well.

[kwicky]

I always thought those lines in the road gave an added check.