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thomas richards


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Hi, I am currently undergoing Advanced Driving lessons with the IAM. My question is to any Road policing bobbies that can spare a few minuets to inform/educate and possibility correct what I have been told?

Motor Vehicles are celebrated by manufacture to under-compensate actual driving speed, and never over. Does that mean' if for instance: I were to be driving and my on-board speedometer read speed at 33 and in actual effect I was driving at 30mp. Would a person (in theory) receive a ticket and be committing an offence. Also should a road camera be set under as a car is?


Many help on this by any Traffic would be appiceated 


Edited by thomas richards
got to incorrect

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Speed detection is based on actual speed, not what an individual speedo indicates.
Road cameras are set to measure the actual speed but an element of 'grace' is used, so no one is going to get a ticket for passing a camera at just over the limit.

Sent from my iPhone using Tapatalk

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If I may say a few words. The reason that most cars speedo is set exact or just under, is to make sure that it's not the car manufactures are not the reason you got time ticket. So if you know that 33mph on your dial is in fact 30mph If you were doing 33mph, and you got a ticket. Don't be surprised. If you drive on the edge of the speed limit every time EG- 33mph in your car. It only takes a fraction of a second just to apply a little to much gas and *FLASH* one lovely mug shot. So here's a tip. Drive your car at 30mph (27.5mph) and you'll never get a ticket. problem solved. thank you.

No offence intended.

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Slow on the mark to respond, the reason your car speedo shows either the actual speed or over the actual speed by up to 10% is set out in legislation (EC ECE Reg39 L120/40 Ref5.3.   https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:42010X0513(03)&from=EN),    it's to allow for some vagaries in manufacture, to allow for tread  wear, small changes of tyre sizes  - hence the list of specific tyre sizes per vehicle rather than your mate's advice on what looks good down the local tyre centre.  
The overall effect on driving and speed limits, is that despite a drivers best efforts, if detected at 38mph (The devices always round down the recorded speed to a whole number),  from the driver's view, the vehicle speedo would show 38mph or up to 10% faster than 38mph.

Some vehicles with both analogue needle and digital displays of the vehicle speed will also differ between the two due to the way they each gather data and how they are viewed - for the needle its usually such a wide needle on such fine markers that they rarely allow you to differentiate your speed by 1mph for example.  Accepting tyre wear etc, digitals tend to show a closer to true speed due to the data used usually comes from the ABS sensors' data
As for doing your IAM or other non police advanced driving course, good for you, but just remember that safe, systematic and smooth driving come long before speed on the learning and application curve. 

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