RSSB2734 - T1155 PERFORM Reviewing the risks and benefits of detonator usage

Detonators are small metal devices that contain a small quantity of explosives, that are placed on the railhead to cause a loud sound, activated by the wheel-rail interface of a passing train to alert the driver they are approaching a hazard on the line ahead (RSSB GE/GN8532, 2015). They were first invented by Edward Alfred Cowper in 1837, to be used as warning or caution devices during fog conditions when signals were difficult to see. The use of detonators has largely remained unchanged since its introduction, over 180 years ago. Detonators are classified as explosives under the 1875 Explosives Act, and the storage of large quantities of more than 5 kgs (approx. 600 detonators) require a licence under the Manufacture and Storage of Explosives Regulations (2004).

The use and placement of railway detonators as a warning and protection method for railway planned and emergency working, has not evolved since they were first introduced. Detonators have a variety of uses, in which the rule book has around 113 references to 'detonator'. Typical uses of detonators include an added layer of protection during the assistance to failed trains, emergency protection arrangements, engineering possessions, protection of isolated sections and during degraded operations. As such, driving cabs are required to have acoustic characteristics that ensure the exploding of detonators is audible to the driver (GM/RT2160), which may inhibit innovative designs and materials.

The placement, handling, storage and transportation of detonators require specific processes, training and competence management. The placement and handling of detonators requires personnel to access the track to place and remove detonators in a systematic and careful manner, adding time to the management and control of a possession. This also exposes staff to risks of trackside working, such as from train movements, electrification hazards, hazardous materials, and slips, trips and falls. As noted in research by RSSB (2007) , although the placement/removal of detonators presents a low risk, the placement/removal of detonators in the wrong place is a medium/high risk, with 36% of the events involving handsignalling identified as high risk.

There have been reports of possession support staff placing detonators on the wrong lines or in the wrong places, exacerbating risks to the placer, working group or activity that require protection. Consequently, safety incidents involving the use of detonators have been reported. In 2008, following a T3 possession, a track worker was stuck by a train and killed when removing detonators and possession limit boards from the line . Although a number of casual and contributor factors were reported, one underlying factor was the requirement for staff the access the track to place and remove protection, including detonators.