>>1655631There are several broad cases for tie material decisions, each of which have different criteria:
The high gross-tonnage Class 1 freight railroad case favors concrete tie in very high gross tonnage territory and heavy curve, moderate-to-heavy gross tonnage territory -- if and only if the life-cycle cost is lower than wood tie. In the western U.S., usually it is. In the eastern U.S., usually it isn't.
The high-speed passenger rail case, e.g., the North-East Corridor and the various new-build projects, favors concrete tie because (1) it wants to minimize time the track is out-of-service for maintenance and concrete tie has a longer replacement cycle; (2) it needs to attain and hold higher track geometry standards, which is easier to do with concrete ties; and (3) it needs to minimize long-term maintenance costs due to funding difficulties.
The light-rail case favors concrete tie because (1) it wants to minimize time the track is out of service for maintenance; (2) maintenance is often occurring on elevated structures or in city streets, which is very costly and disruptive to neighboring land and transportation uses, and (3) it needs to minimize long-term maintenance costs due to funding difficulties.
The branch-line and short-line case will almost always favor wood tie because it cannot economically justify an in-face replacement of wood ties with concrete ties.
The industrial track, new-build case will favor whichever is cheaper on an installed initial-cost basis.
