The　objective　of　this　paper　is　to　evaluate　the　accuracy　of　equations　specified　by　the　current　AASHTO　LRFD　codes　for　highway　concrete　slab-on-girder　bridge　bending　moment　distribution　factors.　A　total　of　645　bridges　were　modeled　and　analyzed　using　the　three-dimensional　finite　element　method.　AASHTO　HS20-44　design　trucks　were　used　in　the　analysis.　The　load　distribution　values　obtained　from　analysis　were　compared　to　the　code　values.　The　results　of　this　investigation　indicate　that　the　AASHTO　LRFD　load　distribution　equations　for　the　interior　girders　of　bridges　with　single-lane　loading,　as　well　as　for　the　exterior　girders　of　bridges　with　two　or　more　design　lanes　loaded,　are　accurate　for　most　practical　cases.　The　accuracy　of　the　code　load　distribution　equations　for　interior　girders　of　bridges　for　the　latter　loading　case　was　found　to　vary　with　deck　overhang,　girder　spacing,　and　span　length.　The　relative　error　in　this　case　ranged　from　5　to　30%　when　compared　with　the　finite　element　method.　The　limits　of　the　overhang　as　specified　by　the　LRFD　Specifications　were　used　in　the　analytical　models.　The　results　of　the　analysis　also　indicate　that　the　relative　errors　caused　by　the　use　of　the　LRFD　load　distribution　equation　for　the　exterior　girder　for　single-lane　loading　may　vary　significantly　with　deck　overhang.　For　example,　this　variation　ranges　from　-25　to　70%　in　this　study.　On　the　basis　of　this　extensive　investigation,　three　new　equations　are　presented　for　the　determination　of　load　distribution　factors　of　the　interior　girders　of　bridges　having　two　or　more　lanes　loaded　and　for　the　exterior　girders　of　bridges　with　single-lane　loading.　Comparisons　between　seven　bridge　load　tests　and　analytical　results　obtained　from　different　theories　show　that　the　proposed　equations　are　conservative　and　reasonably　accurate.　In　addition,　they　are　easy　to　use　and　provide　a　rational　approach　for　strength　evaluation　and　load　rating　of　existing　bridges.