made from other materials only if the material is essential

Full Title

Transverse or longitudinal sleepers; Other means resting directly on the ballastway for supporting rails > made from other materials only if the material is essential

Classification Context

Section:

FIXED CONSTRUCTIONS

Class:

CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES

Subclass:

PERMANENT WAY; PERMANENT-WAY TOOLS; MACHINES FOR MAKING RAILWAYS OF ALL KINDS