This paper explores the influence of the choice of structural analysis method on inventory and operating rating factors calculated using American Association of State Highway and Transportation Officials load rating equations for bridge class culverts. The authors used three increasingly sophisticated, production-oriented structural analysis methods to load rate 86 reinforced concrete box culverts selected to represent the full population of 1855 culvert designs maintained by the Texas Department of Transportation (TxDOT). It is presumed that more complex soil structure interaction models will generate more accurate and less conservative load ratings than simpler models. Results indicate that increasing the model sophistication by using soil springs does not significantly change the inventory rating when compared to the first method. Increasing sophistication further by modeling soil using linear-elastic finite elements yields mixed results, showing an increase in the rating factor for sufficiently high soil moduli of elasticity but a slight decrease in the rating factor for lower soil moduli of elasticity.