North Downs Line - Technical Information

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 through both tunnels between Guildford and Shalford junction since resignalling in October 1999. The entire line is designated W6 gauge and overnight engineering possessions of up to 4.5 hours are available.

• 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 mph (110 km/h), except for two 30 mph (48 km/h) 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) from Aldershot South Junction. The line speed is 70 mph, except for a 40 mph (64 km/h) 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. It is controlled by Guildford from Shalford Junction 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.

At Reading, North Downs Line services normally terminate at platforms 4, 5 and 6 on the south side of the station, although access to other platforms is possible via Reading Spur 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. Formerly, the access to platforms 4a & 4b was via a short single track section, which severely limited capacity. As part of the 2012 Reading resignalling scheme, an additional platform has been provided for North Downs Line services; platforms have consequentially been re-numbered as 4 (former 4a); 5 (former 4b) and 6 (new). The underpass will also be reinstated.

Network SouthEast originally planned to electrify the whole route, with a completion date of 1993 being published, but these plans were dropped.