Green reflective studs on a motorway are found at slip road entry and exit points. They mark where vehicles can safely leave or join the main carriageway and also are used to delineate the edges of lay-bys. Their green color signals permission to diverge from the main carriageway and provides clear guidance in low visibility conditions such as night, fog, or heavy rain. These studs help drivers identify routes on and off the motorway and reduce confusion and hesitation at junctions or slip roads.