Amber reflective studs on a motorway are found along the boundary between the carriageway (road lanes) and the central reservation (the median strip dividing opposing directions of traffic). They mark the right-hand edge of the carriageway on a motorway, helping drivers stay in the correct lane, especially at night or in poor visibility. These amber studs guide drivers to avoid crossing into the central reservation. Other coloured studs indicate different parts of the motorway: red studs mark the left-hand edge, white studs mark lane separations, and green studs mark slip roads or lay-bys. Amber studs are thus specifically positioned next to the central reservation on motorways to improve safety and lane discipline.