why have cars got a white number plate on the front and yellow on the back?

Answer 1

As I said the last time this came up:

The current system came in in 1973, but there was around a decade of trials before that involving various Police forces and the Thames Valley Traction Co among others. The introduction of reflective plates was to improve chances of reading index marks under motorway conditions and the use of yellow for the rear plate was decided after trials.

If a vehicle wasn't used on motorways, reflective plates weren't mandatory. London Transport (and IIRC) Reading Corporation used white on black number plates into the 1980s.

Answer 2

UK number plates are reflective.

The front plate is white with black lettering as that is the most legible.

The rear one cannot be white, as UK laws do not allow any white light source (including reflective surfaces) on the rear of a vehicle (apart from reversing lights), so it is the next most-legible background colour for black lettering - yellow.

Answer 3

So you can tell whether its the front or back of the vehicle.

The colours are chosen to provide contrast - Yellow or white contrast well with black and most countries will use yellow or black backgrounds.

In the UK we used to use white letters on black, again to give a good contrast.

Answer 4

They are an aid when driving at night and in fog. Vehicles should be parked on the left hand side of the road so if you see a white reflector it should be on your right as you pass it and a yellow one should be on your left.

A similar rule applies to those red and white reflective markers you see on country roads, especially on bends - you pass to the left of white ones and to the right of red ones just as you would if they were lights.

Answer 5

The idea was that you could tell which way a car was pointed

Answer 6

So that any photographs will show which direction the car is travelling.

Answer 7

FOLLOW YELLOW BUILT CAR