Based　on　the　analysis　of　driver　overtaking　process　characteristic　and　combined　with　the　overtaking　experiment,　the　driver　gap　acceptance　behaviors　at　the　same　directional　lane　are　studied.　The　experimental　result　indictates　that　the　gap　acceptance　behavior　can　be　described　by　binary　Logit　model.　The　calculation　methods　of　how　to　determine　the　critical　head　space　gap　and　critical　head　time　gap　are　also　put　forward,　and　the　connection　among　the　critical　head　time　gap,　the　critical　head　space　gap　and　the　velocity　is　analyzed.　At　last,　the　conclusion　that　the　drivers　are　more　sensitive　to　head　space　change　than　to　head　time　change　in　the　overtaking　process.