How fast does your speedo say you’re going?

How fast does your speedo say you’re going?

With the Police announcing a zero tolerance to speeding this summer, how do you really know how fast you are going? Is your speedometer really that accurate? Are the police radar guns that accurate? Could I be speeding without actually realising?

The NZ Police say you could be issued a speeding infringement notice this summer if you are doing 1kph over the limit. But the accuracy of car speedometers is not that accurate. However, there is good news here. There is an Australian standard for speedo accuracy on new cars that we also use here in NZ. It says that a speedo should not understate speed at all and should not overstate speed by more than 10% +4kph. This means that when your speedo reads 100kph your actual speed must be between 87.3kph and 100kph. As a result manufacturers set speedos to overstate your speed.

In a recent test by, 60 new cars were tested from cheapies to high end luxury cars. Only four cars were actually travelling at 100kph when the speedo read 100kph. The rest overstated their speed by up to 6%. Tyre wear makes a difference, too. The difference between new and worn tyres is around 3kph at 100kph with the worn tyres actually being slower.

So what about the police equipment? How accurate is it? Well the police gear is tested and calibrated annually so should be pretty accurate, or more accurate than your speedo at least, so I wouldn’t rely on that as a defence when you’re pinged. Officers will be able to use discretion and decide whether to issue a ticket or give a warning so best to be polite if you’re pulled over. Stationary speed cameras will continue to operate at the 4% tolerance.

So the best thing to do when hitting the roads this summer is stick to the speed limit as indicated by your speedo as you are likely to be travelling under the limit. Keep safe. 

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