Wiktionary
single yellow line
n. (context UK English) A single yellow line painted at the side of a road to show that parking is permitted only at specified times.
Wikipedia
Single yellow line
A single yellow line is a road marking that is present on the side of the carriageway in the United Kingdom. It indicates that parking or waiting at that roadside is prohibited at certain times of day. The exact times vary by area and are indicated by signs at the roadside. Stopping to load and to pick up or set down passengers is generally allowed unless additional restrictions apply.
Usage examples of "single yellow line".
As they headed for Branscombe, Kate heard about parish business and the hapless church warden who had pleaded compassionate visiting as an excuse for parking on a single yellow line.