Determining the Cost of Track Maintenance
Date
1993-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Railway Track and Structures
Abstract
A proper understanding of the costs of doing business is essential in any business environment. In the transportation industry generally, and in the railroad industry in particular, this understanding can be difficult to achieve. Railroads carry many different commodities, moving in a variety of cars of different sizes and weights and in trains of varying length, motive power assignments, and maximum operating speeds. The effect on costs of an incremental change in train length, for example, or car weight, can be difficult to predict. While railway costs in general are difficult to predict, maintenance of way costs, and specifically the relationship between maintenance of way costs and critical traffic and right of way parameters, are especially difficult to accurately quantify. This has always been a problem in track maintenance planning accurately determining the rate of failure of track components and, more to the point, accurately determining the cost of maintaining the track structure. These difficulties are due to many factors, not the least of which being the complex relationships between component life or "damage" and external loading and environmental factors. Recent research has shown that many of these relationships are non-linear, such as the non-linear damage effects caused by differing axle loads of various traffics. These non-linear damage effects, in turn, translate into non-linear cost sensitivities. Further compounding the difficulty in defining track maintenance costs are the conflicting trade-offs that are inherent in high density tracks. While high densities may allow for some economies of scale in maintenance of way practices, they also limit maintenance access, which in turn drives up costs. Furthermore, the level of traffic density has a major impact on costs. On lightly used rail lines, increases in traffic can be accommodated with only small increases in the cost of track maintenance. But as traffic continues to increase, the environmental mechanisms that limit track component life when no traffic uses a track (rust and decay) become insignificant on heavily trafficked railroads. Rust and decay are replaced by abrasive wear and crushing; rails and ties do not remain in track long enough for environmental mechanisms to dominate life. Several of the "traditional" railway costing methodologies rely heavily on an economy of density effect, generally in the form of a simple, statistically derived relationship between cost and such gross density parameters as ton-miles or train-miles. Such regression analyses are the traditional and accepted methods for railroad costing, particularly regulatory costing for the Interstate Commerce Commission (ICC) or other regulatory agencies. However, these assumptions can lead to a misspecification of incremental track maintenance costs as traffic density increases. They can further result in an improper allocation of budgetary resources for track maintenance, particularly on the highest density routes which are generally the most sensitive to the level of maintenance and condition of the track. Therefore, it is important to both maintenance of way officers and to senior railroad management that accurate track maintenance costs be obtained and used in the planning and budgeting process. In recent years, research into the mechanisms governing track degradation has indicated that train miles or ton miles are not necessarily adequate as model variables with which changes in costs can be associated. The speed of operation, axle load of the equipment, and key characteristics of the track and traffic are all important determinants of track maintenance costs. The growing understanding of the factors governing track component life has led to the development of much more complex models. Cost models in common use today rely on one of two basic approaches:
•Engineering Cost Models
•Allocation Models
The engineering models are deterministic in nature, relying upon mathematical models of physical deterioration to predict the required quantities of track maintenance, and the application of unit costs to determine total required expenditures. Allocation models, such as regression equations developed from industry wide cross-sectional data, address the allocation of costs between different traffic types on a given railroad or on a given route.
Description
Keywords
Transportation, Railway costs, Track maintenance
Citation
Zarembski, A. M., “Determining the Cost of Track Maintenance”, Railway Track and Structures, April 1993.