Reflective road studs

Road studs do a job that painted lines cannot do at night or in heavy rain: they throw your headlights back at you. Their colour is the information, and the test asks about it directly, because in poor visibility the colour of the studs may be the only thing telling you where the edge of the road is.

The pattern is consistent. White studs sit between the lanes. Red studs mark the left-hand edge of the carriageway. Amber studs mark the right-hand edge, alongside the central reservation of a dual carriageway or motorway. Green studs mark the line across a slip road or a lay-by, where traffic joins and leaves.

A useful way to hold it: if amber is on your right and red is on your left, you are in the correct place on a dual carriageway. Green across your path means an entry or exit, so expect vehicles to cross your line.