12.1 Where these Guidelines require that a particular fitting, material,
appliance or apparatus, or type thereof, should be fitted or carried in a craft, or that
any particular provision should be made, the Administration may allow any other fitting,
material, appliance or apparatus, or type thereof, to be fitted or carried, or any other
provision to be made in the craft, if it is satisfied by trial thereof or otherwise that
such fitting, material, appliance or apparatus, or type thereof, or provision, is at
least as effective as that required by these Guidelines.
12.2 Where compliance with any of the provisions of these Guidelines would
be impractical for reasons of the particular design of the craft, the Administration may
substitute those with alternative provisions, provided that equivalent safety is
achieved. The Administration which allows any such substitution should communicate to
the Organization particulars of these substitutions and the reasons for their
acceptance, which the Organization should circulate to its Member Governments for
information.