Abstarct: Abstract Ground transportation is considered the most important and most used type of transportation for passengers and moving goods. Among the types of ground transportation, roads are the main pillar of ground transportation. On this basis, the quality of road pavement is very important. In this research, the quality of the pavement of the Kerman-Zarand road has been evaluated by the PCI method, and different sections have been marked with different qualities, and then with the help of police speedometer cameras, the speed of light vehicles in each of these points was taken to determine the impact of the pavement quality on the speed. Vehicles should be measured. 34 pieces were selected from the length of the studied route. These pieces were chosen in such a way that they are not in the places of arches, uphills and downhills, and the places close to residential areas were not considered so that the factors of slope, arch and residential area do not affect the speed of free flow.Harvesting conditions for other factors were also done in the same way so that they do not affect the speed or that their effect is minimized, for example, for the effect of atmospheric conditions, harvesting was done on a sunny day. For asphalt pavement failures, there are 17 failures [PAVEMENT MANAGEMENT FOR AIRPORTS, ROADS, AND PARKING LOTSM. Y. Shahin] should be taken into account, of course, according to the section under study, some of these failures may not exist in that part. The damages and severity of each were measured and the impact of each was calculated with the methods fully described in the third chapter, and finally the pavement quality index (PCI) was obtained. Speeds were taken in parts that had different qualities and the effect of quality on the speed of vehicles was investigated and analyzed with the help of SPSS software. The results showed that the quality and speed have a direct relationship with each other and with the increase in the quality of the pavement, the speed of the free flow of passing vehicles also increases.Analyzes in different models such as linear, quadratic, quadratic and was done and the results showed that the best type of modeling for this research is the third-order model with a correlation value of R2=0.661. This type of research can be of great help in predicting failures and thus reducing pavement quality and maintenance costs Keywords: quality - pavement - pavement quality index (PCI) - SPSS software - transportation - pavement failures - free flow speed - modeling - R2 correlation value   was done and the results showed that the best type of modeling for this research is the third-order model with a correlation value of R2=0.661. This type of research can be of great help in predicting failures and thus reducing pavement quality and maintenance costs