Road surface or pavement (American English) is the durable surface material laid down on an area intended for vehicle or foot traffic. It is used primarily as a road surface. Pavement, (British English) generally refers to a sidewalk or walkway. In the past, gravel road surfaces, cobblestone and granite setts were extensively used. These surfaces have mostly been replaced by asphalt or concrete laid on a compacted base course. Road surfaces are frequently marked to guide traffic. Today, permeable paving methods are beginning to be used for low-impact roadways and walkways.