The golden (or bright orange
) rules seem to be as follows:
1) Bags must not obstruct the minimum specified surface areas of high-visibility clothing which may need to be worn (these surface areas being specified in the standards for the clothing). Thus staff who may need to carry equipment in rucksacks over hi-vis vests/jackets whilst on or near the line should be in possession of a bag which replicates the surface of the hi-vis clothing which they are wearing. In addition it is also mandatory for a logo of the employer/training sponsor to be affixed to the rear of hi-vis clothing used on the railway.
2) Bags should not be able to trap the user by getting caught in machinery or a moving train, so they should either be provided with emergency release tabs on the straps, or not need to be worn across the body. (Railway clothing manufactured in line with GO/RT standards conforms to this, either through the stitching or emergency poppers/tabs).
There are some members of train crew, such as conductors who do not have to access their trains using walking routes through rolling stock depots, who wouldn't routinely have to carry equipment trackside. For this reason the TOC may choose to issue bags in black or company colours, which often hide dirt better than orange ones and therefore look smarter. However, anyone who routinely has to carry their job's equipment in a bag (such as a rucksack) across the body should be provided with protective equipment which replicates the appropriate level of visibility and snag resistance.
There would appear to be a fair amount of flexibility across the different TOCs regarding people using and wearing their own bags. Some TOCs insist on a disclaimer being signed for any incidents arising as a result of the employee's own bag. Others simply monitor whether it could cover hi-vis clothing or if it could entangle the employee in machinery. Some people do not find the standard hi-vis rucksacks to be particularly ergonomic or suit their work well, so it may be less distracting and more efficient to use a different bag. Even some bags used for specific roles on the railway are supplied in designs somewhat different from the ubiquitous orange crew bag - consider the blue COSS or lookout bags supplied to some NR / contractor staff, for example.
