The purpose of this project has been generally two-fold. First, it has been to determine equivalencies for tridem type axle loads. At the present time a set of tridem axles is considered a tandem axle if the center to- center spacing of the outer axles is 8 feet or less and it is considered a tandem plus a single axle load if the spacing is greater than 8 feet. Using the load equivalency factors for single and tandem axle loads developed from the AASHO Road Test equations, this method of evaluating a tridem axel load results in a wide variation in equivalency between an axle spacing of 7.9 feet and 3.1 feet. Tins is not reasonable and, therefore, the purpose of this study has been to determine what equivalency
values are appropriate and how they should vary with axle spacing.
