From Open Risk Manual
Barries include mechanisms for stopping, slowing down, restricting, limiting or in some other way weakening an uncontrollable process.
- Material barriers are physical hindrances (buildings, walls, fences, railings, cages or gates) aiming to prevent physical linkages and/or access
- Functional barriers prevent or hinder actions by setting preconditions for actions (locks, passwords)
- Symbolic barriers require an act of interpretation by an intelligent agent that responds or reacts to it. Examples are for instance coding (color, shape, spatial layout), instructions, procedures, signs or an approval of some sort.
- Incorporeal barriers are not physically present in the current situation; they depend on the knowledge of the user. Common incorporeal barriers are rules, guidelines, restrictions and laws.
- Barrier analysis as a design tool in complex safety critical systems Blomkvist et al,