In much of the world, national or local governments fund public roadways and highways, in part, by charging an annual fee to every vehicle owner. To prove the vehicle owners have paid the fee, a metal plate with a unique identification is affixed to the rear or front bumper (often both) of the vehicle (this also gives a useful way of identifying each vehicle). Usually, the identification is a short string of random or semi-random figures, letters or both. Sometimes, the first few or last few digits may identify the sub-region where the car is registered, but usually the digits are assigned sequentially.