###### Abstract  
The optimal preventive maintenance timing of traditional asphalt pavement is based on the maximum benefit-cost ratio. For cost evaluation indicators, mainly agency cost and user cost, use life cycle cost analysis (LCCA) to determine. The environmental impact of pavement preventive maintenance activities is often overlooked. For the benefit evaluation index, only the new area under the performance curve is used to express the maintenance benefit, and the benefit evaluation index is single. This study proposes an integrated approach combining life cycle assessment (LCA) and LCCA to model preventive maintenance timing decisions considering economic, social, and environmental factors. In this paper, LCA is used to quantitatively analyze the energy consumption and emissions in the pavement operation and maintenance process, and the environmental costs are also included in the accounting scope of the costs. The costs that constitute pavement use are analyzed from three aspects: the agency cost, the user cost, and the environmental cost. At the same time, in the process of constructing the cost model, the costs caused by the maintenance construction process to users and the environment are also taken into consideration. Aiming at the benefit index and comprehensively considering the economic benefits, social benefits, and environmental benefits brought by maintenance, a comprehensive evaluation model of maintenance benefits was constructed based on the analytic hierarchy process (AHP). On the basis of accurately calculating the cost and benefit of maintenance in the life cycle, the model of the optimal preventive maintenance timing of asphalt pavement is constructed so as to calculate the optimal timing of preventive maintenance and provide certain information for the formulation of expressway pavement preventive maintenance programs. For reference. Taking a highway project in China as an example to verify the applicability of the model  
preventive maintenance; maintenance timing; LCCA; LCA; maintenance benefit; benefit-cost ratio 202330  
and obtain more maintenance benefits. The timing of preventive maintenance is usually determined by maximizing the benefit-cost ratio. The purpose of cost analysis is to select the best plan through an economic comparison of different preventive maintenance timing plans. LCCA refers to the method of selecting the optimal solution for economic indicators by calculating and analyzing the various costs incurred by all feasible solutions throughout the life cycle, including agency costs and user costs [4]. With the richness of theory and the success of practice, more and more decision-makers have begun to use the life-cycle cost analysis method to make pavement maintenance decisions [5]. When making maintenance timing decisions, cost components ignore user costs or exclude key components of user costs for simplicity [6; 7; 8; 9]. During the life-cycle stage of pavement, user costs can be divided into two categories. Normal operating costs and work zone costs. Normal operating costs occur during the normal lifetime of the pavement and are primarily a function of the pavement surface condition for a given road geometry and topography. Work zone costs are due to work zones installed during initial construction or maintenance activities. In the current economic evaluation method, there are relatively mature methods for estimating agency costs and normal operating costs, but there are relatively few studies on work zone costs. This part of the cost is also often overlooked when performing a life-cycle cost analysis. Research [6; 7; 8; 9] has determined the timing of preventive maintenance, but in the cost calculation, they have not considered the cost issues caused by the maintenance construction process for users. Such an incomplete LCCA may lead to biased results. At present, the calculation of highway pavement maintenance benefits is mainly based on the pavement performance decay law.