NR NR/SIN/141 ISSUE 1 PDF

The SIN applies to all Automatic Half Barrier (AHB) crossings that fulfil all of the following critera:

• Where there is more than one track over the level crossing;
• The level crossing has only single direction controls on one or more of the tracks over the crossing;
• The crossing strike-in controls incorporate treadles without directional discrimination, acting in "independent Treadle and track circuit" configuration without a reset timer.

These AHB crossings have similar attributes to Athelney AHB at the time of the incident.

Purpose

The purpose of this Special Inspection Notice (SIN) is to mandate actions to mitigate maloperation of AHB crossings after controls have been perturbed, for example by engineering train movements.