Variations from the two general types of bridge deck construction consist of track rails
anchored directly to steel or concrete-slab superstructures (direct fixation) and the
several types of concrete-encased beam spans or concrete-filled steel-trough
superstructures on which the ballast section is placed. The latter types of structures
have many examples still in service today, but are not generally cost-effective for new
construction.
Some might consider the notion of bridge railings to be an odd bridge design
consideration. Railway bridges traditionally have not been designed for the conveyance
of anything other than railway traffic, which does not in and of itself, require any sort
of railing whatsoever. Recently, however, a greater focus upon railway worker safety
has resulted in railings being widely incorporated.