Double Line Automatic Signalling is a form of
railway signal
A railway signal is a visual display device that conveys instructions or provides warning of instructions regarding the driver’s authority to proceed. The driver interprets the signal's indication and acts accordingly. Typically, a signal mi ...
ling used on the majority of
double line
A double-track railway usually involves running one track in each direction, compared to a single-track railway where trains in both directions share the same track.
Overview
In the earliest days of railways in the United Kingdom, most li ...
sections in
New Zealand. Double Line Automatic Signalling uses
track circuits to detect the presence of trains in sections broken up by intermediate
signals. Usually there is an 'up' and a 'down' main line, and beyond station limits the lines are not
bi-directionally signalled. DLAS is not designed for wrong-line running in emergency situations.
[{{Cite web , url=https://www.taic.org.nz/inquiry/ro-2008-110 , title=Report 08-110 train control operating irregularity leading to potential low-speed, head-on collision Amokura 23 September 2008 , access-date=28 November 2020]
Junctions or points
At junctions or points, one of or both mains signals are usually controlled either remotely (by a Train Controller or Signalmen) or switched in at a local panel.
Sidings
Sidings off one or both mains are usually operated by switchlock lever points secured by padlock and track circuit presence that enables a release to be given before points can be operated.
Areas of use
* Papakura - Amokura
* Te Kauwhata - Hamilton.
* Trentham - Kaiwharawhara
* Kaiwharawhara - South Junction
* North Junction - Waikanae
* Islington - Heathcote
Formerly double line
* Islington - Rolleston
* Mosgiel - St Leonards
References
Railway signalling
Railway signalling in New Zealand