What do these zigzag white lines mean?

Zigzag lines at pedestrian crossings

The zigzag road markings at pedestrian crossings are to ensure drivers and pedestrians can see each other clearly.

You must not park your vehicle within these markings, either before or after the crossing.

You must not overtake a moving motor vehicle within the zigzag marked area before the crossing.

You must not overtake a vehicle that has stopped next to the crossing either to obey signals or because pedestrians are using the crossing.

If you are in a queue of vehicles extending over a crossing, keep the crossing clear and look out for pedestrians on the road.

Crossings for cyclists and horse riders also have zigzag markings, and the above rules apply there too.

See the UK Highway code, Rules 191-199, for more on pedestrian crossings.