RSSB2752 - T1167 - WP3 - Preventing irregular train movements into a possession - Tender Deadline Extended To 4th January 12:00 Mid-Day

A railway possession occurs when it is necessary for Network Rail to restrict access to part of the network so that engineering work can take place to maintain or renew the asset. Consequently, passenger and freight trains will typically have restricted access on one or more lines, for work to be undertaken directly on or near the line. Such work may include the use of engineering trains or on-track plant within the possession.

The time in which a possession is taken will vary depending on the nature of work undertaken. To support safe working within a possession, guidance and requirements are available in the RSSB Rule Book Module T3 Possession of a running line for engineering work (2016). Part of current possession protection arrangements include the use of possession limit boards (PLB) and detonators as warning and protection methods. Detonators have been used in the rail industry for over 180 years. They are small metal devices containing a small quantity of explosives, to be placed on the track, intended to warn personnel of potential hazards on the line ahead. Detonators are placed alongside PLBs, which is a red stop sign with a steady or flashing light visible on both sides of the board. This is used to identify the boundary of the possession, and if a train passes a PLB without authority it is considered a signal passed at danger (SPAD). PLBs may also be used as part of the protection for a line blockage. Within the possession, work-site marker boards are also placed to indicate the exit of a worksite and passing without authority is also considered a SPAD.

The PLB should clearly identify the possession boundary to control access into a possession. As such, PLBs should be visible, readable, and interpretable to train drivers and possession staff . The design of PLBs should also consider a variety of factors that may influence the interpretability and readability of PLBs, including train speed once movement authority has been given by the signaller to approach the possession, PLB position, lamp luminosity, contrast to the background, ambient light, external light sources, track curvature, and rolling stock cab design.

The placing and removing of detonators and PLBs require staff to access the track, which exposes them to risks of trackside working, including train movements, slips, trips and falls. There have also been reports of possession support staff placing detonators and PLBs on the wrong lines or in the wrong places. An investigation into possession protection irregularities identified nine categories of irregular events that could have been harmful to staff, possibly resulting in fatality (RAIB, 2015) . These events include protection equipment incorrectly placed, working outside a protected area, trains incorrectly signalled into a protection, and work carried without protection.