scope:

Introduction

GK/RT0051 (ref. 1) describes various signalling methods of ensuring that only one train is present in a singled-ended single line section at any one time, such as tokens, staffs and axle counters. However, this paper is confined to the method known as "One-train System Without Train Staff" (OTW).

The type of OTW described in SSI8003-80 is limited to that employing Intermediate Train Detection (as defined in GK/RT0051) at the section exit, this being used where the Signaller is located remote from the exit and comprehensive train detection covering the whole section is not provided. Intermediate Train Detection employs three train detection devices, a sequence of operations of which are used to prove a train has exited the section.

Only panel operated OTW is currently covered - non-panel operation will be added later.

OTW can only be used where there are no train-shut-in facilities on the single line. An alternative method using a single ended axle counter section is the preferred option for such a line as this permits Track Circuit Block regulation on the adjacent lines to be extended to the single line section. However, OTW has to be used where the number of vehicles in the train may change whilst the train is on the single line, i.e. as occurs with freight trains.