Eyesight Reqirements

To drive a motor vehicle you must be able to read a car number plate, in good daylight, from 20.5 metres (67ft) for the older style (pre 1st Sept 2001) or 20.0m for the new narrow style plates.

If you wear contacts or glasses to see this distance then they should be worn when driving.  Within the practical test the candidate has to read a number plate from the prescribed distance.