|2011 - July - Burrows & Stringer - Folding Signal Posts - Myth or Practical Solution|
Stephen Burrows CEng MICE
Adelaide Rail Leader, Aurecon
Peter Stringer FIRSE
Signalling Accreditation Manager, Aurecon
Since time immemorial, signalling systems have made use of stiff, upright, highly robust and immovable signal posts for good practical engineering reasons. They should be able to withstand environmental conditions like rain, wind and snow without excessive deflection and still remain upright to support that vital signal arm or head with the associated aspect.
Back in the good old days, signal engineers didn't even bother with the mechanical or civil engineer to help with the signal post or foundation design! More recently, the mechanical and civil engineers have got involved and we now have good foundations and strong posts that satisfy the various railways' specifications.
Times have also changed with regards to Operational Health and Safety (OH&S). Legislation hasn't always been so onerous and signalling personnel were routinely permitted to work two metres above the ground without a safety harness. It was nothing to expect a maintainer to climb a 12.5m tall lattice post to maintain or repair a piece of mechanical equipment such as pulleys or cranks or replace a light bulb which had expired.
So in today's safety conscious environment and with the widespread introduction of 25kV overhead line equipment above the track, is it really desirable to have maintenance staff working at heights and in close proximity to lethal electrified equipment? Somewhat surprisingly, the answer to this question is "yes" and the vast majority of new signals continue to be installed on conventional straight posts.
Several alternative solutions are available which allow all maintenance activities to be undertaken at ground level using folding, hinged or sliding posts. These solutions also provide significant safety benefits yet the signalling industry is slow to embrace them. Is there genuine justification for this reluctance to change or is the signalling industry simply intolerant to change?