The　purpose　of　this　research　is　to　interpret　the　behavior　of　highway　bridge　decks　due　to　the　impact　of　moving　vehicles.　First,　the　analytical　theory　is　briefly　presented,　including　the　vehicle　model,　bridge　model,　road　surface　model,　and　numerical　methods.　Both　the　vehicle　and　the　bridge　are　simulated　as　thre-dimensional　constructs.　The　road　profile　is　modeled　using　a　stationary　Gaussian　random　process　that　is　described　by　a　power　spectral　density　(PSD)　function.　Newmark＇s　direct　integration　method　is　used　in　the　bridge　dynamic　analysis.　The　bridge　deck　free　and　forced　vibration　characteristics,　including　the　impact　factors　of　moment　and　shear　with　both　single　and　multiple　trucks　traveling　over　a　rough　deck,　are　investigated.　Then,　the　stiffness　effects　of　the　longitudinal　girders　are　studied.　Analytical　results　show　that　the　dynamic　loading　of　the　bridge　deck　is　significantly　smaller　than　that　of　the　longitudinal　girders　as　the　direction　of　the　deck　main　internal　forces　is　perpendicular　to　the　vehicle　travel　direction.　The　research　results　are　applicable　to　bridge　deck　design.　©　2013　American　Society　of　Civil　Engineers.