This paper involves the estimation of a model of railway road and equipment capital stocks and the changes in their levels that have occurred since 1983. The model is based on balancing the level of investment and the level of degradation of the capital stocks to create a data series for roadway capital and for equipment capital. A two-stage least squares errors in variables model is applied. This is appropriate as degradation and exact constant dollar investment are not directly observable. Results obtained from the model indicate that Class I railroads have increased their absolute capital stock levels over the period examined. This holds for both roadway and equipment capital although roadway capital has increased at a somewhat faster rate.