Today's truck configurations, weights, dimensions, axle types, axle loads, tire types, and tire pressures are very different from those used in earlier studies. Thus, their impacts on pavements must be studied and re-examined. Also the traditional use of load equivalencies in determining the impacts of these trucks is questionable. The problem being researched in this book pertains to developing an improved understanding of heavy vehicles, environment, and highway pavement interactions, and using that understanding to assess impacts of alternative truck configurations and develop LEFs. A 3D finite element program is used to model moving truck loadings on highway pavement systems under various environmental conditions. The pavement responses are used to develop LEFs as well as performance curves. The load equivalencies and performance curves are then used to assess the damage characteristics of different pavement systems under numerous traffic loadings and environmental conditions. The methodology and results discussed in this book will be helpful to the highway pavement community: researchers, practitioners, and policy makers.