NR SSI8003-82 ISSUE 1 PDF

Introduction

Additional safeguards against irregular operation of track circuits may be required in areas where track circuit operation cannot be relied upon, e.g. areas prone to leaf-fall contamination. Failure of a track circuit to detect a train can lead both to false aspect clearance, and to improper operation of comprehensive approach locking or TORR look-backs. (Wrongful release of route locking ahead of a train is already protected against - see SSI8003- 10F.)

This document provides a data method for dealing with such areas of poor track circuit operation, and builds on that already employed in the Woking control area where sequential proving of track circuits was specifically introduced to address the problem of false aspect clearance in areas prone to leaf-fall contamination.

The areas where sequential proving of track circuits are required are expected to be identified on the signalling scheme plans. It is also expected that additional control tables will be prepared to specifically define the sequential proving controls required.