The requirements for safety in railway are well defined in EN 50129, EN 50126 and EN 50128. You will be required to meet these standards for an ISA (independent safety authority) to give a positive report, and then for the applicable transportation authority to grant revenue service authorization. As you can imagine, the willingness of a given passenger to take a certain amount of risk is not part of the process described in these standards.

EDIT: theses standards are applied worldwide, despite the EN prefix.

EDIT: good reference site: http://en50126.blogspot.it/2008/07/velkommen.html?m=1