Technical Requirements
4.4 Protruding Objects.
4.4.1* General. Objects projecting from
walls (for example, telephones) with their leading edges between 27 in and
80 in (685 mm and 2030 mm) above the finished floor shall protrude no more
than 4 in (100 mm) into walks, halls, corridors, passageways, or aisles (see
Fig. 8(a)).
Objects mounted with their leading edges at or below 27 in (685 mm) above
the finished floor may protrude any amount (see Fig. 8(a)
and (b)).
Free-standing objects mounted on posts or pylons may overhang 12 in (305
mm) maximum from 27 in to 80 in (685 mm to 2030 mm) above the ground or finished
floor (see Fig. 8(c)
and (d)).
Protruding objects shall not reduce the clear width of an accessible route
or maneuvering space (see Fig. 8(e)).
Appendix Note
4.4.2 Head Room. Walks, halls, corridors, passageways,
aisles, or other circulation spaces shall have 80 in (2030 mm) minimum clear
head room (see Fig. 8(a)).
If vertical clearance of an area adjoining an accessible route is reduced
to less than 80 in (nominal dimension), a barrier to warn blind or visually-impaired
persons shall be provided (see Fig. 8(c-1)).