## 1 Introduction  
The accurate assessment of pavement deflection is a critical factor in ensuring road safety and extending the lifespan of roads. The Falling Weight Deflectometer (FWD), currently the most widely used device for pavement deflection measurement, applies a fixed pulse load to simulate the actual loading of moving vehicles, enabling a precise deflection measurement of the pavement [1]. It has also been widely studied for evaluating pavement modulus and deformation behavior [2]. However, FWD operation is limited to static measurements and requires temporary road closures, which hinders its efficiency and convenience [3]. In contrast, the Traffic Speed Deflectometer (TSD), based on the laser Doppler effect, was jointly developed by the Danish Road Directorate and Greenwood Engineering in the 1990s. Due to its operational safety, high efficiency, and ability to continuously collect data, TSD has been widely adopted globally [4]. TSD not only significantly improves the safety and efficiency of measurement operations, but its continuous data acquisition also offers excellent accuracy and resolution, making it particularly suitable for large-scale network evaluations [5, 6, 7, 8, 9]. In recent years, numerous scholars have conducted in-depth studies on the precise assessment of traditional asphalt pavements using TSD. [PERSON] et al. [PERSON] et al. (2010) evaluated various deflection algorithms and dynamic analysis models based on TSD deflection slope data. The results indicated that the deflection indices generated by all the algorithms were similar, making them applicable for estimating the residual structural capacity of traditional pavement structures at the network level. [PERSON] et al. [PERSON] et al. (2011), using the Semi-Analytical Finite Element Method (SAFEM), simulated the dynamic load on flexible pavements with viscoelastic asphalt layers. They studied the effect of pavement roughness on TSD measurements and highlighted the need to develop correction methods for TSD deflection measurements on rough pavements. [PERSON] et al. [PERSON] et al. (2012) used the finite element method, considering the nonlinear stress dependence of unbonded granular materials and fine-grained soils with transverse isotropy, to study the impact on TSD deflection slope results and pavement performance predictions. Despite the global application and research on TSD technology, its applicability and measurement accuracy on specific pavement structures have not been fully validated. [PERSON] et al. [PERSON] et al. (2013) found that the 7 m deflection basin assumption proposed during TSD development does not apply to commonly used semi-rigid base asphalt pavements in China. Their calculations revealed that the deflection error caused by the TSD calibration sensor can reach 87.3%. Further analysis [PERSON] et al. (2014) revealed that these pavements exhibit a \"three-peak\" deflection slope curve, which shifts to a \"single-peak\" profile under subgrade-induced longitudinal cracking, with deflection slope peaks increasing by an order of magnitude. However, investigations into the current pavement conditions in China reveal that semi-rigid base pavements exhibit structural failure within their design lifespan ([PERSON] et al., 2015; [PERSON] et al., 2015). This is due to the combined effect of load and environmental factors, which causes cement-stabilized materials to crack easily, and the cracks will propagate to the road surface, ultimately leading to reflection cracks across the entire surface ([PERSON] et al., 2015; [PERSON] et al., 2015). To prevent the occurrence of reflective cracks on the pavement, researchers have designed an inverted asphalt pavement structure ([PERSON] et al., 2015). Similar designs have been reported in countries such as South Africa, Australia, Brazil, and parts of the United States.