A　huge　number　of　exiting　highway　bridges　are　in　decay　due　to　age,　misuse,　lack　of　repair,　and　in　some　cases,　because　they　were　not　designed　to　meet　current　demands.　There　is　a　growing　interest　in　ensuring　that　the　bridges　continue　to　function　well　and　even　improve　to　meet　increasing　demands.　The　aim　of　the　research　reported　here　is　to　present　and　apply　a　dynamics-based　performance　evaluation　procedure　to　the　exiting　highway　bridges.　The　procedures　are　briefly　explained　including　bridge　description,　analytical　finite　element　modeling,　field　ambient　vibration　testing,　model　calibration　and　performance　evaluation.　The　case　study　is　a　continuous　steel　girder　bridge　on　interstate　1-24　in　Western　Kentucky,　USA.　The　seismic　performance　and　retrofitting　is　evaluated.　The　proposed　dynamics-based　performance　evaluation　procedure　can　be　applied　to　a　wide　range　of　existing　bridges.