by the M4) having in Surrey the Sunbury-on-Thames, M25 interchange and Lightwater/Bagshot junctions. M23 (north–south) in effect connects Croydon to Brighton as the dualled A23 trunk road to the north and beyond Crawley. It has junction to a spur to Gatwick Airport on the Surrey/Sussex border. It has a Surrey junction, the M25 Merstham interchange, close to the Reigate M25 junction. Other major roads include: The A3 trunk road from Portsmouth to London. The road now bypasses and historically assisted in the growth of Haslemere, Godalming, Guildford, Esher and Kingston upon Thames. The Hindhead Tunnel bypasses a former bottleneck at Hindhead and the Devil's Punchbowl. The A24 from London to Littlehampton and Worthing. In Surrey, it passes through or around Ewell, Epsom, Ashtead, Leatherhead and Dorking. It passes Box Hill, near Dorking. Unlike the A3, which is almost completely dual carriageway, the A24 is, apart from a central Surrey stretch, single carriageway; it bypasses Leatherhead, Dorking and Horsham. The A31 trunk road west from Guildford to Bere Regis via Farnham and is connected to the M3 near Winchester and via the A331 near Aldershot. It is dual carriageway along the Hog's Back from the A3 to Farnham. It is one of the ancient routes from London to Winchester, see Pilgrims' Way. The short A331 connects the A31 to the M3. It runs along the Surrey-Hampshire border, bypassing Aldershot, Frimley and Farnborough. Rail Much of Surrey lies within the London commuter belt with regular services into Central London. South Western Railway is the sole train operator in Elmbridge, Runnymede, Spelthorne, Surrey Heath, Woking and Waverley, and the main train operator in the Borough of Guildford, running regular services into and regional services towards the south coast and South west. Southern is the main train operator in Mole Valley, Epsom and Ewell and Reigate and Banstead and the sole train operator in Tandridge, providing services into and . There are many railway lines in the county, those of note include the Waterloo to Reading Line, South West Main Line, Portsmouth Direct Line, Sutton and Mole Valley Lines (from Horsham, West Sussex itself on the Arun Valley Line from Littlehampton) and the Brighton Main Line. The Waterloo to Reading Line calls at , , and in Surrey. The South West Main Line calls at and up to six other Surrey stops including . The Portsmouth Direct Line is significant in linking , and