In plain English
The zigzags protect the sightline at a crossing. A parked car here hides pedestrians from drivers and drivers from pedestrians — so nothing may stop or overtake.
Where you'll see it
On both approaches to zebra, pelican, puffin and toucan crossings.
The common trap
Stopping "just for a second" to drop someone off. Even a brief stop on the zigzags hides a child stepping out — and it's an offence.
Memory anchor
Zigzags are the crossing's no-go zone: if the paint is jagged, keep moving and don't overtake.