Pre - registration inspections, conducted before registration of a vehicle, should also incorporate a speedometer check.

Inaccurate speedos mean that many motorists are unaware they are speeding. Vehicles fitted with larger wheels may render a speedometer inaccurate. While roadworthy regulations limit increases in diameters of modified wheels, not all motorists who install larger wheels are aware these do fewer revolutions to achieve the same speed. Unless the speedo is calibrated, it could be registering 50kmh while the car is actually clocking up 60kmh. The motorist could be caught and fined and the car declared unroadworthy because the tyres are 15mm larger than the originals.

Also low tyre pressure could also lead to inaccurate readings, as could the load being carried or fitting of non-standard or modified gearboxes and differentials& even worse, many cars are simply fitted with inaccurate speedometers.

Vehicle manufacturers must comply with Australian Design Rule (ADR) 18/01 Instrumentation, which specifies vehicles should be fitted with odometers that are accurate to +/-10% above 40kmh. At +10%, a speedo will register 55kmh when the car is actually travelling at 50kmh, and 110kmh, and actually travelling at 100kmh.

Keep in mind that a speedometer can go unchecked for the life of a car, regardless of the number of registration transfers, because pre-registration inspections do not demand speedos be tested for accuracy.