North Downs Line
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North Downs Line

Legend Great Western Main Line Reading Reading (Southern) River Kennet Earley River Loddon Winnersh Triangle Winnersh M4 Wokingham (Wokingham level crossing – B3349) Reading to Waterloo Line Crowthorne Sandhurst Blackwater M3 Farnborough North Farnborough (Main) South Western Main Line Farnborough Airfield North Camp Ash Lock Aldershot Alton Line Aldershot South Jn Basingstoke Canal Tongham (1856-1937) Ash Ash Green Halt (Ash level crossing – A323) Ash Junction Wanborough (closed December 1960) Guildford Portsmouth Direct Line River Wey New Guildford Line Shalford (Chilworth West level crossing – A248) (Chilworth East level crossing – unclass.) Chilworth (level crossing – unclass.) Shere Heath (1849-1850) Gomshall Dorking West Dorking (Deepdene) Dorking Mole Valley Line Spur closed 1946 River Mole (Brockham level crossing – unclass.) Betchworth Quarry Betchworth (Betchworth level crossing – B2032) (Reigate level crossing – A217) Reigate Redhill Brighton Main Line Tonbridge Line

The North Downs Line is the name of the passenger train service connecting Reading, on the Great Western Main Line, to Gatwick Airport, on the Brighton Main Line. It is also the name used to refer to the line over which these services run between Reading and Redhill,^[1] which was authorised by Acts of Parliament in 1846 and 1847 and constructed by the Reading, Guildford and Reigate Railway (RG&RR), opening in 1849. The stated objective of the company was to

"secure through traffic passing between the West, North and Midlands and the Channel Ports avoiding the congestion of London and thus saving time, distance and expense."^[2]

The line runs parallel to the North Downs escarpment between Ash and Redhill. The South Eastern Railway which operated the line from its opening, ran passenger services on the line from Reading to London Charing Cross via Redhill and even today, the distances along the line are measured from the terminus of the former SER.

Technical information

The line is two track throughout, except for a short single track section on the approach to Reading. Reversible working is provided on the down line between Guildford and Shalford. The entire line is designated W6 gauge and overnight engineering possessions of up to 4.5 hours are available.^[1]

• Reading to Wokingham is electrified (3rd rail, 750 V DC) and signalled under the TCB (Track circuit block) system from Wokingham Signal Box. Signalling headways are 3 minutes for fast services and 3.5 minutes for stopping services. The line speed is 70 miles per hour (mph), except for two 30 mph restrictions (on the approach to Reading and through Wokingham station).
• Wokingham to North Camp is also under the control of Wokingham Signal Box, however long distances between signals increase headways to 6 minutes and 11 minutes for fast and stopping services respectively (the longest headways on the line). This section is not electrified and the line speed is 70 mph.
• North Camp to Shalford Junction is controlled from Guildford (TCB). Signalling headways are 2 minutes with an additional 1 minute added for stopping services. This section is electrified (3rd rail, 750 V DC) and the line speed is 70 mph, except for a 40 mph restriction at Ash Junction (between Ash and Wanborough) where the line curves sharply, and a 30 mph restriction on the approaches to Guildford station.
• Shalford Junction to Reigate The route leaves the Portsmouth Direct Line at Shalford Junction and there is a 20 mph restriction. From here to Reigate the line is not electrified and is controlled by Guildford to Gomshall and by Reigate Signal Box (TCB) from Gomshall to Redhill. Signalling headways are 5 minutes for fast trains and 7 minutes for stopping services. The line speed varies from 30 mph (on the approach to Shalford junction) to 70 mph.
• Redhill to Reigate is electrified (3rd rail, 750 V DC). The approach to Redhill is controlled by Three Bridges Signalling Centre and has a 30 mph speed restriction.

The major capacity constraints are the platform capacities of Reading, Redhill and Gatwick Airport stations. ^{[3] [4] [5]}.

At Reading, North Downs Line services normally terminate in platforms 4a and 4b on the south side of the station, although access to other platforms is possible via a junction with the Great Western Main Line (see map, right). Trains could formerly access the north side of Reading station via an underpass, although this has been disused for some time. The access to platforms 4a and 4b is via a short single track section, which severely limits capacity. As part of the 2012 Reading resignalling scheme, an additional platform will be provided for North Downs Line services. The underpass may also be reinstated.^[6]

Network SouthEast originally planned to electrify the whole route, with a complet