| By the end of 2020,the length of highways in China had reached 161,000 kilometers,ranking first in the world.The "71118" network of seven capital radiate lines,11 north-south vertical lines and 18 east-west horizontal lines has been basically completed.At present,many highways have been damaged by cracks,permanent deformations,pits and grooves,etc.,which are closely related to the increasing traffic and the formation of channelized traffic.It can be predicted that in the coming years,China's highways management will shift from the era of large-scale construction to a period of construction and maintenance,and gradually to a new period of maintenance management.It is expected that during the 14th five-year plan period,the demand for highway construction and maintenance in most provinces and cities will reach the overall balance,and the demand for maintenance will exceed the demand for construction in some eastern regions.Highway maintenance project can be divided into preventive maintenance,repair maintenance,special maintenance,and emergency maintenance according to maintenance purposes and maintenance objects.Repair maintenance is the main object of maintenance management system.The research of pavement maintenance management in western countries has an earlier origin.Since the Pavement Management System(PMS)was developed by the University of Texas in the United States,Canada,Denmark,the United Kingdom,and other countries had successively developed their own pavement management systems to the mid-1980s.China began this research in the 1980s.The first China Pavement Management System(CPMS)has been applied in many provinces and cities which has accumulated valuable experience.With the deepening of research,scholars' research on maintenance management not only focuses on the development of management system,but also explores each stage of pavement management.By studying on the existing research,this paper finds that the related research of highway maintenance management and benefit has the following points need to be further discussed.(1)The evaluation model of current standard is greatly influenced by subjective factors,and its weight of evaluation index is fixed,while the evaluation results are not consistent with the actual road condition.Mathematical models such as neural network,genetic algorithm evaluation method which can improve the accuracy of the pavement performance evaluation,but are difficult to apply in the daily maintenance management work due to the difficulty of modeling.(2)Decision-making models based on analytic hierarchy process,mathematical programming method,genetic algorithm and other methods all focus on the needs of road maintenance,and the maintenance benefits are not included in the research.Benefit analysis,however,uses the method of new area under the performance curve to express the maintenance benefit,which has a single evaluation index.It only focuses on the maintenance benefit and cost,ignoring the actual conditions and needs of the pavements.(3)The research on the benefit of highway maintenance project is very limited.An analysis system for the multiple benefits of highway pavement maintenance needs to be established.(4)After the implementation of the highway maintenance decision,the whole maintenance benefit analysis can guide the decision-making of the next maintenance cycle scientifically and effectively.However,in the existing literature,there is no relevant research on using the results of maintenance benefit analysis to guide maintenance decision-making.In order to solve the above problems,this paper mainly focuses on the following three aspects:Firstly,the evaluation process of highway maintenance management is optimized by Extension Neural Network(ENN)to improve the accuracy and reliability of the evaluation.Secondly,on the basis of the evaluation results,a bi-level programming model was built to optimize the decision-making process which takes the maximization of the maintenance benefit(the sum of the operator benefit and the user benefit)and the minimization of the user travel cost as the objective functions.Finally,after the implementation of pavement maintenance decision,a benefit analysis system is established to analyse the actual benefits(operator benefit,user benefit,environmental benefit and national economic benefit)generated by maintenance project.The following conclusions are drawn:(1)ENN model can be well applied to pavement maintenance management to improve the accuracy of pavement performance evaluation.Its structure is simple;the number of input nodes and output nodes can be determined only by the number of feature vectors and the category of evaluation results.Its initial weights can be obtained from the training data to avoid the problem of long learning time.It has high learning rate,fast convergence,high fault tolerance ability and strong generalization ability;it can maintain high accuracy even in the case of noise interference and insufficient training samples.(2)A bi-level programming model was built for pavement maintenance decision-making.The maximization of the operator's toll revenue increasing and the user's vehicle travel cost savings is taken as the objective function of the upper model,and the minimization of the vehicle travel cost is taken as the objective function of the lower model.By the using of this model to optimize pavement maintenance decision-making process,decision can be made by combining subjective and objective factors such as traffic,geological conditions,importance degree in the road network,construction conditions and so on.The advantages of it are easy model structure,clear objective function,and strong operability.(3)Establish a highway pavement maintenance benefit analysis system that integrates operator benefit,user benefit,environmental benefit,and national economic benefit.Regression analysis method and synthetic control method were used to analyse the above benefits.Among them,the operator benefit is reflected in the increase of toll revenue.The user benefit is reflected in the travel cost saving of highway users,including the travel cost saving,time cost saving and safety cost saving.Environmental benefit reflected in the reduction of environmental costs,including the reduction of gas emissions and traffic noise.The national economic benefit is reflected in the increase of output and the reduction of urben unemployment rate.The quantitative study of pavement maintenance benefit is realized.This paper has done innovative work in the following aspects:(1)This paper introduced the ENN model into the pavement maintenance management by the compatison of many evaluation methods.It can complete the classification by both model state recognition and extension state recognition with high accuracy and strong abilities of fault tolerant and generalization.Besides,this model is simple to set up,and convenient for the actual operation of highway operation department.(2)This paper optimized the pavement maintenance decision-making process on the basis of existing theory.The using of bi-level programming model avoids the malpractice that the traditional decision-making process only faces the maintenance section and neglects the maintenance benefit.By comparing with the cost-benefit analysis method,it avoids the safety hazard caused by excluding the road sections with poor pavement performance from the maintenance list.(3)Based on the stakeholder theory,this paper tried to divide the stakeholders of highway maintenance projects,and establish a benefit analysis system integrating operator benefit,user benefit,environment benefit and national economy benefit.In the analysis of national economic benefit,the synthetic control method is innovatively introduced to simulate the "counterfactual" economic effect of the five cities which are not intervened by highway maintenance project. |
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