To figure out the primary factors that significantly impact the sustainability of highway routine maintenance management (HRMM), this paper examined 23 highway operating subsidiaries (evaluated decision-making units, DMUs) affiliated with Shaanxi Transportation Holding Group (STHG) in Shaanxi Province as an example. First, data envelopment analysis (DEA) was used to evaluate the performance of HRMM for each DMU. Subsequently, a truncated regression model was utilized to analyze the primary factors that impact the outcomes of HRMM. The conclusions indicated that except for the widely recognized input and output factors, there exist some uncontrollable factors that can affect HRMM efficiency, including the amount of natural dustfall, urbanization rate, tunnel length, and bridge length. These findings offer suggestions for STHG focusing on DMUs facing challenges with high dustfall and urbanization rate and long bridges and tunnels when allocating maintenance resources to improve HRMM efficiency and achieve sustainable highway maintenance management. Moreover, the methodology for analyzing uncontrollable factors can also serve as a valuable reference for other maintenance types or fields, contributing to the broader goal of promoting sustainability in transportation infrastructure development.