This study presents the downstream and upstream truss behaviour of a through type newly constructed steel bridge. The modal parameter variation of truss joints of bridge with variable vehicle speed effects have been worked out to determine their flexibility. The testing on the steel bridge was carried out with the same instrument setup on upstream and downstream trusses of bridge subjected to three different speed of the same vehicle. The comparison of the changes in the frequency, mode shape, mode shape curvature and modal strain energy with respect to both the trusses and analytical model has been presented. It has been concluded that upstream and downstream truss of the bridge can behave in different manner even if designed for same loading due to constructional variations and the vehicle movement. The difficulty of modal parameter extraction of the particular bridge under study increased with the increase in speed due to decreased excitation time.