In Taiwan,both the engineers and temporary employees serving in National Freeway Bureau are graduates of civil engineering.The lack of specialization in the pavement domains as students and the increasing financial requirement of pavement maintenance are hindering new engineers from further improving their knowledge on pavement.The present study aimed to improve the comfort index of national freeways.First,the inspection aspects of national freeways,such as road testing items and methods,are analyzed.Subsequently,the lack of previous literature on this subject prompted the researchers to organize relevant information pertaining to the comfort index and inspection processes of national freeways.The inspection and analysis of national freeways are beneficial for maintaining and enhancing the comfort and quality of national freeways.Moreover,the International Roughness Index is adopted to elucidate the differences exhibited at different speeds.In addition,the present study endeavored to determine skid number(SN) degradation equations to improve road traffic safety.First,a correlation analysis between SN and traffic flow,as well as between SN and climate data,was performed.Findings revealed an increased correlation between SN and traffic flow,while the correlation between SN and climate(temperature and rainfall) is less prevalent.Subsequently,traffic flow and climate were adopted as the factors for the SN degradation equations.The present study divided the traffic flow data of the entire national freeway system into five groups,enabling researchers to present individual SN degradation equations for various traffic flow conditions,thereby contributing to maintain and elevate the road traffic safety of national freeways. In Taiwan, both the engineers and temporary employees serving in National Freeway Bureau are graduates of civil engineering. The lack of specialization in the pavement domains as students and the increasing financial requirement of pavement maintenance are hindering new engineers from further improving their knowledge on pavement. The present study aimed to improve the comfort index of national freeways. First, the inspection aspects of national freeways, such as road testing items and methods, are analyzed. Published, the lack of previous literature on this subject prompted the researchers to organize relevant information pertaining to the comfort index and inspection processes of national freeways.The inspection and analysis of national freeways are beneficial for maintaining and enhancing the comfort and quality of national freeways. Moreover, the International Roughness Index is adopted to elucidate the differences demonstrated at different speeds. In addition, the present study endeavored to d etermine skid number (SN) degradation equations to improve road traffic safety. First, a correlation analysis between SN and traffic flow, as well as between SN and climate data, was performed. Findings revealed an increased correlation between SN and traffic flow, while the correlation between SN and climate (temperature and rainfall) is less prevalent.Subsequently, traffic flow and climate were adopted as the factors for the SN degradation equations. the present study divided the traffic flow data of the entire national freeway system into five groups, enabling researchers to present individual SN degradation equations for various traffic flow conditions, so contributing to maintain and elevate the road traffic safety of national freeways.