South Western Railway operates services between London Waterloo and Leatherhead via Raynes Park and Epsom.

Half continue along the main line to Dorking, others run to Guildford via Bookham and Effingham Junction.

The route from Raynes Park to Horsham via Epsom and Dorking (including the Bookham Branch) is known to commuters as the Mole Valley Line – seven out of the 15 stations are in the Surrey district of Mole Valley.

Signalling between London Victoria and Ewell East (including the Epsom Downs Branch) is controlled by London Victoria (VC); between London Waterloo and Box Hill and Westhumble by Wimbledon (W); between Box Hill and Westhumble and Warnham by Dorking (CBK); and between West Croydon & Waddon and Warnham & Horsham by Three Bridges Signalling Centre (T).

It is 524 yards (479 m) long and runs through the lower chalk of Norbury Park, entering the hillside immediately north of one of the three viaducts over the River Mole.

[14] Restrictions imposed by the landowner, Thomas Grissell, meant that vertical ventilation shafts could not be constructed and the tunnel portals were given lavish architectural treatment.