Spedo accuracy

[Pesky jones]

Say you're going 80mph, does anyone know if your're actually going 80? Or less?

[Matthewsimone]

http://click2how.com/your-speedometer-wrong-can-drive-faster/

[StuF]

My digital speedo reads 80 mph where my analogue gauge shows around 72/74mph  when on the motorway
Digital one is more accurate I guess!

[xjay1337]

Say you're going 80mph, does anyone know if your're actually going 80? Or less?

My dash says 80 my Polar MFD which is wheel speed sensor says 75

[lukemk5gti]

I've always wondered this after seeing one of those speed digital display signs showing a different speed to what I'm doing.

At least by the looks of that link you're actually travelling slower than your speedo shows.

I might have cruise control on at 100km/hr in a 100km/hr zone and when I see a speed camera I still hit the breaks on occasion thinking what if the speedo is wrong!!

[xjay1337]

The European regulation, ECE-R 39, states that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70).

You will never be going faster than your displayed speed.

[usmangti]

The European regulation, ECE-R 39, states that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70).

You will never be going faster than your displayed speed.

Is it also true that a camera or speed gun can only catch you above the speed limit after 10% plus 2mph? Ie in a 30 would have to be driving at least 35mph?

[xjay1337]

CPS recommend only pursuing cases where the speed is 10% + 2.
You can (technically) be done for doing 1mph over the speed limit. But practically it won't happen.

[andyR43]

The European regulation, ECE-R 39, states that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70).

You will never be going faster than your displayed speed.

Is it also true that a camera or speed gun can only catch you above the speed limit after 10% plus 2mph? Ie in a 30 would have to be driving at least 35mph?

I had to attend a speed awareness course for travelling at 33mph in a 30mph zone. Caught by a camera van, just after pulling away from traffic lights and the road merging from 2 lanes into 1 so filtering into the traffic!!!