information The line is two-track throughout and is designated W6 loading gauge. Overnight engineering possessions of up to hours are available. Reading to Wokingham is electrified (3rd rail, 750 V DC) and signalled under the track circuit block system from Wokingham Signal Box. Signalling headways are 3 minutes for fast services and minutes for stopping services. The line speed is , except for two restrictions (on the approach to Reading and through Wokingham station). Wokingham to North Camp is also under the control of Wokingham Signal Box, although 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. It is currently planned to transfer the control of Wokingham Signal Box to the new Rail Operating Centre in Basingstoke in 2024. North Camp to Shalford Junction is controlled from Guildford (TCB). Signalling headways are 2 minutes for fast services and 3 minutes 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 restriction at Ash Junction (between Ash and Wanborough) where the line curves sharply, and a 30 mph restriction on the approaches to Guildford station. Resignalling in October 1999 enabled reversible working on the down line through both tunnels between Guildford and Shalford Junction. 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