The reflective studs on a motorway are color-coded to convey specific information:
- White studs are the most common and are used to mark the separation between lanes on a motorway.
- Red studs mark the edge of the motorway on the left-hand side, between the leftmost lane and the hard shoulder.
- Amber studs indicate the central reservation, marking the edge on the right-hand side.
- Green studs are found between the main carriageway and slip roads, indicating the beginning or end of slip roads where vehicles enter or exit the motorway.
- Fluorescent green/yellow studs are used to indicate temporary roadworks or changes to the motorway layout.
Therefore, the reflective studs that mark the lanes on the motorway itself are primarily white. The studs that indicate a slip road, specifically, are green.
