The　purpose　of　this　paper　is　to　study　the　saturation　flow　rate　and　its　adjustment　factors　which　is　the　basis　of　estimating　the　signalized　intersection　capacity.　Based　on　the　field　data,　the　passenger　car　equivalences　are　calculated　using　the　time　headway　method,　which　is　adopted　to　analyze　the　effect　of　different　type　vehicles　on　the　saturation　flow　rates.　In　order　to　determine　the　effect　of　lane　width　on　the　saturation　flow　rate,　a　regression　model　is　developed　and　the　adjustment　factor　for　lane　width　is　obtained.　The　approach　grade　effect　on　the　saturation　flow　rate　is　studied　and　the　adjustment　factor　for　approach　grade　is　provided.　The　multiple　regression　method　is　used　to　analyze　the　right-turn　vehicle　effect　on　the　through-turn　shared　lane　saturation　flow　rate　and　the　adjustment　factor　for　right　turn　is　suggested.