 On this line, it passes the Sunbury Common part of that town and the south side of the slightly larger town of Ashford, as Staines Road West and a dual carriageway, passing the Queen Mary Reservoir to form the by-pass to the large town of Staines-upon-Thames, after which it goes back to single carriageway to turn briefly south-west to take the high street roads network, rather than a straight continuation, which becomes the A30, then ends this street as Clarence Street, crosses the Thames (for a second time) at Staines Bridge, and resumes its main third-part orientation.It crosses the M25 motorway, that has a large cross-river junction at Junction 13, north of Egham.The road turns north-west, as Windsor Road, in the middle of Runnymede's meadows, with its National Trust buildings and memorials, before leaving Surrey and entering Berkshire.