Double Line Automatic (DLA)

All movements are controlled by fixed signals under the Automatic Signalling Regulations. Signals can be either automatic or operated by a signalman. Some stations can be switched out, converting the mainline running signals to automatic operation. Points are usually power operated - exceptions are switchlocked sidings and switchstands.

All running signals are Three-Position and have either two units or a top unit and a Marker. Multi-unit signals provide more aspects than the three available with a single three-position unit. An illuminated A-Light amends the rules applicable to the signal.

Single Line Automatic (SLA)

Timetable authority and a clear Departure signal are required to enter a single line section. The points are hand operated. The 1965 Single Line Automatic Signalling Regulations are quite complicated - they were written before the use of radio communication.

Running signals are Three-Position and have a top unit and a marker for the lower unit (i.e. the lower unit is fixed red). Signals operate automatically.

To depart from the Loop the Releasing Switch is used to clear the Departure signal. The intermediate signal shows yellow if an opposing train in the next section (double yellow). An illuminated L-light on the Arrival signal indicates that the points are set for the loop.

Centralised Traffic Control (CTC)

A clear Departure signal is sufficient authority to enter a single-line section. The signals and power points are operated from Train Control in Wellington. The only remaining traditional CTC panel is at Upper Hutt.

All running signals are Three-Position and have either two units or a top unit and a Marker. Multi-unit signals provide more aspects than the three available with a single three-position unit.

In the 1988 Rule Book there is a separate set of CTC Regulations; in the 1965 book there is a single set of Automatic Signalling Regulations.

Track Warrant Control (TWC)

A track warrant issued by Train Control is required for all movements in TWC territory, whether on the single line or at a crossing loop. There are three types of loop - manual, points indicator and arrival signals. The majority of loops use points indicators, although there is a programme to install Arrival signals. Points at indicator and arrival signal loops are power operated. Both the Loop and Main are track circuited. (Right Indicator Loop).

Operating procedures are defined in the Generic Track Warrant Regulations.

Station Limits

All movements are authorised by the signalman - either by fixed signals or verbally. Includes the remaining pocket of two-position working at Masterton. Also pockets such as Kaikoura (?) which are controlled from Train Control.

Station Limits section under construction.