Asphalt　pavement　distress　at　the　bus　stop　is　one　of　the　major　distresses　of　urban　roads　in　populated　areas　-　intensive　metropolitan　zones.　In　order　to　analyze　the　cause　of　this　kind　of　road　distress　in　Beijing　City,　the　vibration　loads　caused　by　buses　are　studied.　Firstly,　the　vibration　acceleration　of　the　asphalt　pavement　at　the　bus　stop　was　measured　on　the　field.　Secondly,　the　vibration　signal　at　three　states,　such　as　the　state　before　buses　coming　to　the　stop　(defined　as　N1　state),　the　state　when　buses　are　idle　at　the　stop　(defined　as　N2　state)　and　the　state　when　buses　start　to　leave　the　stop　(defined　as　N3　state).　These　were　modeled　by　a　power　spectrum　analysis　scheme　separately.　Thirdly,　quantitative　comparisons　were　made　among　the　three　kinds　of　dynamic　signals　measured　at　the　above　three　states.　Finally,　a　tentative　conclusion　is　deduced,　that　is,　one　of　the　key　factors　which　cause　asphalt　pavement　early　distress　should　be　the　dynamic　load　which　is　produced　by　bus　performance　characteristics　at　the　time　of　starting　to　leave　the　stop.　This　specific　dynamic　load　frequency　lies　between　the　50∼60HZ　band.　©　2010　ASCE.