The　impact　behavior　of　a　multigirder　concrete　bridge　under　single　and　multiple　moving　vehicles　is　studied　based　on　correlated　road　surface　characteristics.　The　bridge　structure　is　modeled　as　grillage　beam　system.　A　3D　nonlinear　vehicle　model　with　eleven　degrees　of　freedom　is　utilized　according　to　the　HS20-44　truck　design　loading　in　the　American　Association　of　State　Highway　and　Transportation　Officials　(AASHTO)　specifications.　A　triangle　correlation　model　is　introduced　to　generate　four　classes　of　longitudinal　road　surface　roughness　as　multi-correlated　random　processes　along　deck　transverse　direction.　On　the　basis　of　a　correlation　length　of　approximately　half　the　bridge　width,　the　upper　limits　of　impact　factors　obtained　under　confidence　level　of　95　percent　and　side-by-side　three-truck　loading　provide　probability-based　evidence　for　the　evaluation　of　AASHTO　specifications.　The　analytical　results　indicate　that　a　better　transverse　correlation　among　road　surface　roughness　generally　leads　to　slightly　higher　impact　factors.　Suggestions　are　made　for　the　routine　maintenance　of　this　type　of　highway　bridges.