What do green motorway studs signify?

Answer: A — sliproad

Green motorway studs signify a sliproad. Green motorway studs are used to mark sliproads on motorways, which are used to join two different roadways together. They are not used to mark the edge of the road, as this is usually marked by white studs or lines. They are also not used to indicate a pedestrian crossing, as these are marked by zebra crossings or traffic lights. Green motorway studs are also not used to mark a cycling lane, as these are typically marked by painted lines or signs on the road.