As an active member of a heritage railway connected to the main line, this has been an interesting thread.
I'm encouraged that those who are active understand the constraints that are in place. What many of the posts from non-active members or just visitors either ignore - or don't even know - is that volunteers are covered by the same Health and Safety at Work Act as employees. Thus as pointed out you cannot just sign a disclaimer.
If an accident happens being, sued by a personal injury claim is the least of a railways worries. If the injury is reportable to the HSE then there is every possibility of a fine or sanctions via that route, regardless of the hypothetical claims in advance that people won't sue.
To be honest, visitors and members demanding the right to spontaneously visit sheds is very disruptive. Where I volunteer we have little time at weekends to achieve a set of activities that are needed to keep parts of the railway operational as we still work for a living. Stopping welding, grinding etc. constantly to allow groups to wander through can mean the difference between a loco being repaired and not.
On one occasion due to an over zealous station member offering to show someone around a shed without prior warning we had to suspend a hydrotest on a boiler we really needed to get back in use.
Open weekends with tours are far more effective as we can ensure walkways are clear for all, items that need to be barriers are, and that the visitors get a better experience which is why we are there. And the majority of visitors are just that, families having a nice day out.
There are many older members who say they'd never get work done if we followed health and safety, and if they decide to leave that sometimes is a good thing, but likewise people who work in industry and want to volunteer are often put off by inadequate facilities by modern standards and a poor health and safety culture exhibited by the older members.
Gone are the days of grandfather rights and risking injury just so they can get to the bothie for a tea break. Railways are hazardous environments and need safety management systems and competencies like any other industry. It may not be popular with some, but the changes I've seen in the last 15 years are all positive. We now have competencies and grade cards, a safety management system and railway standard rules and exams.
Working with volunteers is always more challenging than employees, but if the volunteers understand why the rules and controls are in place - the legal requirement for the railway to protect them and the public - they usually come onside. For those that cannot or will not understand this, then maybe there is no longer a place for these people as active volunteers.
BigB