Vibration monitoring (operational modal analysis) and vibration testing (modal analysis) of constructed systems for identifying their dynamic characteristics are becoming more common, however, vibration monitoring/testing that actually helped enable critical management decisions by the owners and operators of constructed systems are rare and in many cases the results of such tests remain "academic." Successful vibration monitoring/testing requires the integration of expertise both in theoretical and experimental structural dynamics as well as in the domain of the constructed system that is being studied. In this paper, two application examples on highway bridges by Drexel University researchers are introduced. In the case of the highly deteriorated Smithers Bridge, the flexibility obtained by MIMO testing by impact was validated by static truck load testing under proof-load levels. The bridge deflections based on the modal flexibility and the deflections measured from truck load test correlated very well, indicating that MIMO testing, if properly designed, executed and processed, can serve as a bridge management tool. In the case of the long-span Burlington-Bristol movable lift-bridge, one tower span exhibited larger operational vibration amplitudes than its symmetric counterpart. After conducting ambient vibration testing of the entire bridge, followed by vibration testing of the piers, the FEM calibrated by the measured dynamic properties was utilized to conduct time-history numerical simulation used for confirming the phenomenon. Both examples reveal that there may be wider application prospects of vibration-monitoring/testing by qualified engineers, if they integrate experimental structural dynamics expertise and constructed system domain knowledge, in order to support operational and maintenance management.