The yellow zig zag lines do not have to be centred on the school gates; they merely have to be outside a school.
The may range from 25.5 metres to 45.5 metres in length.
There must be a TRO (Traffic Regulation Order) in place for them to be enforced. As establishing a TRO can be a relatively expensive process, many highway authortis merely painted on the lines withoutt allowing for enforcement powers
The line prohibit the stopping of any vehicle during the times shown on the adjacent sign(s). this applies to all vehicles and includes school buses (contyrary to the belief and practice of mant schools).
The function is to provide a lenght of road with clear line of sight to allow pedestrians and drivers to see each other without obstruction.
These lines are enforceable by the Policxe and not PCSOs or CEOs. Thus stopping during the prescribed times is a criminal offence.