NR NB 139 ISSUE 4 PDF

This guidance applies to all track circuits on electrified and non-electrified lines and advises for the provision of insulated IRJs for S&C and the associated track circuit bonding to be

undertaken in the style generally expected for electrified railways. The benefits which accrue are:

• a reduction in the risk associated with rail end breaks by the reduction in the number of insulated rail joints;

• S&C ‘strengthening’ from the improved positioning of insulated rail joints within and adjacent to S&C units;

• a reduction in track circuit bonding ‘complexity’ by removing the requirement for a continuous, series-bonded signalling rail;

• consistency of design approach whether electrified or not;

• a proven significant reduction in EMC-related influences such as track circuit residual voltage in most circumstances and the removal of the need to provide

additional track circuit relays at first-design.

A non compliance is required to deploy these arrangements: an approved Tracker exists [12983] which covers multiple sites on the Western Route.

This Notice Board advises signalling project engineers and designers to discuss with RAM Signalling and RAM Track to decide when the approach described in this document is appropriate.

Purpose

This Notice Board provides guidance in the preferred approach to the bonding of jointed d.c. track circuits in switches and crossings [S&C]: the principal benefit is to whole-life asset

performance by the reduction in the potential for rail breaks from a decrease in the quantities of insulated rail joints [IRJs]. The effect of electrical interaction between adjacent track circuits is

also reduced, obviating the need for feed-end relays in most circumstances. This is a second Notice Board on the theme of track circuit bonding. It is a Safe by Design initiative and has

been endorsed by the relevant functional heads. This Notice Board forms its own briefing note. A worked example is attached as a separate pdf file.