In　this　study,　the　delay　of　buses　at　bus　stops　is　defined　and　classified.　According　to　this　classification,　parameters　that　result　in　bus　delay　are　then　proposed.　A　concept　of　＇bus　arrival　occupancy　rate＇　is　also　introduced　in　this　study　to　quantitatively　explain　the　situation　at　a　bus　stop　with　reference　to　a　typical　bus　stop　in　Beijing.　A　relationship　is　then　established　between　bus　delay　and　bus　arrival　occupancy　rate.　The　study　also　proposes　a　delay　estimation　model　for　buses　at　two　types　of　bus　stops:　a　bus　bay　and　a　curbside　bus　stop.　©　2009　ASCE.