Cruise control

[gdallas]

Was cruising down the a90 today at 78 when I noticed a camera van. Don't think I slowed down in time. Think it's enough to book me? I understood the tolerance to be 10 percent plus 2. Thoughts? Anyone been done at simmilar speeds by a van?

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[Guest 2]

I always thought the 10% was a myth?

[gdallas]

I hope not! So angry with myself. This table over at daily mail agrees with my understanding of 10 percent plus two mph, but take that with a pinch of salt! New speed camera guidelines allow drivers to go 86mph and escape fines | Mail Online

Fingers are crossed

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[_tones]

The 10% plus 2mph is based on police guidelines... The camera should hopefully take this into account. Let us know what happens and if you hear anything.

Road Traffic Offences: Guidance on Fixed Penalty Notices

[gdallas]

I will do. It was a flat Road so the cruise control was definitely at 78. Note marked in diary two weeks from now. Will report back either way

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[Embisix]

Sussex use 10% +3 and most other authorities use +2. Cameras are calibrated with these tolerances but a radar gun isn't, so it's at the operator's discretion. As long as you passed a camera and not a hairdryer I'd say you'll be fine.

I know this because I have recently attended a (very interesting and beneficial) speed awareness course after being tugged at 86.

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[richlean]

If yours is anything like my B8, the speedometer reads about 2-3 mph high at those speeds when compared with a GPS. So your indicated 78 was probably more like 75-76.

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[_tones]

Yeah, mine also reads a few mph higher than GPS. There is another myth which relates to speeding guidelines where the speedo can be up to 10% out but must be reading above the speed you are actually doing so you can't be going quicker than you think you are. The 2mph is the governments own tolerance figure added on top...

[Tabletski]

The 10% was based on the old 1960 and 1972 Road Traffic Acts which stated speedo was to be accurate +/- 10%.
This changed in 1988 to the speedometer must be accurate.
I always thought the 10% was built in because of this. But, about 10 years ago I had a sporting acquaintance who was a police inspector, he mentioned that his force used a speed based on their statistics of drivers caught. He said if they set it low they caught too many people, which caused admin and enforcement difficulties, eg. The office sending out tickets could only practically send out a certain amount of tickets in a working day.




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[rafletcher]

The 10% was based on the old 1960 and 1972 Road Traffic Acts which stated speedo was to be accurate +/- 10%.
This changed in 1988 to the speedometer must be accurate

Wrong. See below, from the 2003 EU regs on Speedometers...

5.2.5.The vehicle is tested at the following speeds:

Maximum design speed (Vmax) of the vehicle specified by the vehicle manufacturer (km/h)	Test speed (V1) (km/h)
Vmax £ 45	80 % of Vmax
45 < Vmax £ 100	40 km/h and 80 % Vmax (if the resulting speed is ³ 55 km/h)
100 < Vmax £ 150	40 km/h, 80 km/h and 80 % Vmax (if the resulting speed is ³ 100 km/h)
150 < Vmax	40 km/h, 80 km/h and 120 km/h

5.2.6.the test instrumentation used for measuring the true vehicle speed shall be accurate to " 0.5 per cent;5.2.6.1.the surface of a test track when used shall be flat and dry, and provide sufficient adhesion;5.2.6.2.if a roller dynamometer is used for the test, the diameter of the roller should be at least 0.4 m; 5.3.The speed indicated shall not be less than the true speed of the vehicle.At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V₁ ) and the true speed (V₂).

0 £ (V₁ - V₂) £ 0.1 V₂ + 4 km/h

So speed displayed V1- actual speed 2 (speedo cannot read less that actual speed) must have a value of between 0 (accurate) and +10% of actual speed + 4kmh. So that's why the Police enforce the way they do.