To realize the relationship between traffic flow and occupancy of the national freeway system in Taiwan, this study analyzes the statistical distributions of traffic flow and occupancy data collected by vehicle detectors of the Freeway No. 1. The Kolmogorov-Smirnov test was adopted to test and analyze the statistical distributions of traffic flow by individual occupancy intervals, and the statistical distributions of occupancy by individual traffic flow levels. The numerical study results indicate that the traffic flow in individual occupancy intervals shows a normal distribution. We deduce that the expected value can present traffic flow in individual occupancy intervals. In addition, the mean value and mode value of traffic flow in individual occupancy intervals exhibits a continuous two-region concave curve relationship. The findings of this study would have policy implications for the freeway bureau in conducting related traffic control strategies and providing road users with traffic bottleneck information for traffic rerouting and other purposes.