Methodology to Validate Traffic Speed Deflection Devices (TSDDs) Measurements Using Laser Doppler Vibrometers (LDV) Sensors

Abstract

Pavement structural evaluation is important for effective pavement management and design. Traffic Speed Deflection Devices (TSDDs) provide an efficient way to collect pavement structural condition data at the network-level. However, the integration of TSDD measurements into pavement management and design applications remains limited due to the lack of standardized data validity procedures. This research proposes a methodology to verify TSDs deflection velocity measurements using non-contact multi-Laser Doppler Vibrometers (LDVs) as traceable reference sensors. The multi-LDV system, consisting of sensors similar to those used in TSDs operating within the United States, enables direct one-to-one comparisons without requiring additional data transformations. The research started with the instrumentation of the Virginia Accelerated Pavement Testing (APT) facility with an LDV sensor to measure pavement deflection velocity under moving wheel loads. By applying the same measurement principles as TSDs, this setup provided a way to assess pavement structural response without requiring embedded sensors. Results showed consistent LDV measurements, which supported the use of LDVs for deflection velocity data collection. The ability to capture pavement response in real time without surface disruption highlights the potential of LDVs to verify TSDs measurements. The effort continued with the validation of LDV measurements using a calibrated three-dimensional visco-elastic finite element (3D-FE) model developed in Abaqus. The model simulated dynamic pavement response under APT loading conditions, incorporating visco-elastic material properties, three-dimensional contact stresses, and continuous moving loads. The LDV measurements agreed with the simulated values, supporting the use of LDVs for measuring deflection velocities. Finally, the multi-LDV system was tried at the Virginia Smart Road facility to directly compare deflection velocity measurements collected by TSDs. Simultaneous data collection allowed for a one-to-one comparison, with results showing alignment between the two systems. These findings suggested that LDVs can serve as reference sensors for TSD data verification, offering a non-contact, non-intrusive and portable approach for pavement monitoring. This methodology provides a framework for State Departments of Transportation (DOTs) and service providers to develop procedures for TSDs verification and certification, supporting pavement management and design practices.