The reflective studs between a motorway and its slip road are green.

Quick answer

On UK motorways, green reflective studs (cat’s eyes) mark the boundary between the main carriageway and its slip roads (entry and exit). These help drivers see where to join or leave the motorway in the dark or in poor visibility.

Why they are green

  • Green studs are specifically designated in the Highway Code to show slip roads and other junction points where traffic can enter or leave the motorway.
  • At night, in rain, fog, or spray, the green reflections stand out from the white lane studs, giving a clear visual cue that you’re approaching an on‑ or off‑slip.

Other motorway stud colours (for context)

  • White: Between lanes and along the centre of normal roads.
  • Red: Left edge of the carriageway, usually next to the hard shoulder or verge.
  • Amber: Along the central reservation (the right edge of the carriageway on a dual carriageway or motorway).
  • Green/yellow: Temporary layouts, such as roadworks or contraflows.

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Find out what colour the reflective studs are between a motorway and a slip road (answer: green), why they are used, and how they fit into the wider system of motorway stud colours for safe driving.

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