The A25 road is one of the two cross-sector non-motorway grade roads in the 2 sector (or Zone 2) of Great Britain alongside the A27 which is approximately double its length along the south coast. It carries traffic from Guildford in Surrey eastward through Dorking along the southern edge of the North Downs, i.e. the Vale of Holmesdale, between that range and the Greensand Ridge to reach mid-west Kent. En route, the road passes through Reigate, Redhill, Nutfield, Bletchingley, Godstone, Oxted, Westerham, Brasted, Sevenoaks and Borough Green. It passes over six of the seven rivers which drain the vale and land to the south, in separate catchments. A short distance beyond Borough Green, at Wrotham Heath, Platt, Kent the A25 ends at a junction with the A20, which continues eastward towards Maidstone.