The allocation of common track maintenance costs among the many traffics using a typical mainline railroad has long been the subject of vigorous debate. As maximum weights for freight cars have increased, and contract passenger service (both Amtrak and commuter) has expanded, it has become increasingly important to properly allocate track costs among traffics.
ZETA-TECH has developed a maintenance of way costing methodology that takes into account the differing loads imposed on the track structure by different types of traffic, and allocates costs based on the damage caused (and consequently the costs incurred) by each traffic type.
This methodology makes use of engineering equations that take into account both traffic characteristics (such as axle load and speed) and track characteristics such as weight of rail, curvature, and grade. These equations are used to produce "weighting factors" that relate the damage caused to a particular track segment by a particular traffic to the "reference" damage caused to reference track by the reference traffic. The reference damage factor is always defined as 1.0; damage factors for other traffics and track types may be larger or smaller than unity.
The weighting factors are used directly to adjust system average track maintenance costs (as defined by model users). The weighted costs reflect actual damage done to the track by each traffic type.
A key assumption in the ZETA-TECH methodology is that certain track maintenance costs (rail, ties, and ballast) are 100% variable with traffic, and that these costs are linearly related to traffic volume at mainline traffic densities (above 25 MGT per year).
This methodology has been applied successfully on several Class I railroads, both to allocate costs among freight traffics and to allocate costs between freight and passenger trains using the same tracks. For a major U.S. railroad, the methodology was used to determine the incremental maintenance of way costs associated with the operation of passenger trains. For another U.S. Class I company, MOW costs were allocated between heavy axle load unit coal trains and other traffic using the line. For a third, costs were produced by line segment for a total of ten traffic types.
The ZETA-TECH methodology is readily adaptable to a variety of traffic mixes. For example; costs can easily be divided between commuter trains and local freight traffic sharing a common track.