This study investigates the dynamic coupling effects on frequency shifts in vehicle-bridge interaction (VBI) systems, with a focus on their implications for the vehicle-scanning method (VSM). A combined theoretical and experimental approach is used to characterise the coupled frequencies of the system. Theoretical derivations show how dynamic coupling influences the identified frequencies of both the vehicle and the bridge. Experimental validation is performed using a laboratory setup consisting of a test vehicle with tunable frequency and a simply supported steel beam. Results reveal that heavier vehicles lead to underestimated bridge frequencies and overestimated vehicle frequencies due to increased coupling effects. The rolling frequency of the wheel is identified in the vehicle spectrum for the first time, demonstrating its proportional relationship to vehicle speed. Parametric studies highlight the effect of vehicle mass and speed on the coupled frequencies and their intervals. Numerical analyses complement the experiments, confirming the theoretical predictions. The results emphasise the need to account for dynamic coupling in practical VSM applications. If frequency shifts are incorrectly interpreted, this could lead to inaccurate assessments of bridge condition. The study proposes design recommendations for test vehicles, including optimal mass and stiffness configurations. This multidisciplinary approach bridges the gap between theoretical modeling and practical implementation. By integrating VBI effects into VSM, the research advances indirect methods for bridge monitoring. Future research should explore non-linear dynamic behaviors and more complex bridge configurations. These insights contribute to improving the reliability and efficiency of indirect bridge monitoring systems. The integration of tunable test vehicles and advanced VBI modeling offers significant potential for real-world applications.