Measures to be taken to improve track circuits shunting sensitivity

Summary

The purpose of this leaflet is to make recommendations to improve track circuit shunting sensitivity.

A summary description of track circuit functioning is given in point 1. The problem of shunting, which constitutes one of the critical points for rolling stock and track circuit compatibility, is explained in point 2.

Point 3 sets out the conditions to be met as regards the voltage to be applied to tracks to ensure, generally speaking, the correct shunting of track circuits. These conditions, already established in the previous edition of this leaflet, cover most of the situations concerning low-traffic lines which are subject to heavy pollution.

Point 4 describes a set of solutions to track circuit shunting problems when the pollution is less severe.

Point 5 looks briefly at the changing constraints associated with developments in rolling stock, running quality and traffic.

These variations are taken into account in the recommendations made in point 6 to improve track circuit shunting sensitivity according to the operating conditions of the lines and the tasks performed by the track circuit.

Point 7 makes further recommendations regarding accreditation of new rolling stock, designed to prevent in-service problems relating to track circuit shunting.

Point 8 looks at the particular case of sanding, which can cause track circuit shunting to fail if no precautions have been taken.