One of the problems with the instantaneous speed control systems is that the speed of passing cars is only checked at certain points of the track and drivers' behavior is not at all possible. The main objective of this research is to evaluate the effect of speed reduction by installing average speed cameras in rural roads. In this study, using the statistical models of the hypothesis testing and the time series, the rate of vehicle speed decrease was compared to the non-camera mode and the speed changes after installing and setting up average speed cameras have been investigated. The studied roadways have average speed cameras, and the information and timing of these cameras have been received from the Road Maintenance and Transportation Organization. In general, the average speed of vehicles before the installation of cameras was 89.66 kilometer per hour and after the installation of cameras was 84.08, which shows a decrease of 58.5 kilometer per hour. The mean percentage of average reduction was 25.5 percent which indicates an acceptable level. According to the results of the test, at the 95 percent confidence level, in the six axes of the nine axes examined, the average vehicle speed decreased significantly. This does not mean that there were no decrease in other axes, but that speed was not significantly reduced. On the whole, the effect of average speed cameras on vehicle speed reduction on roadways with lower traffic volume was higher than that of high-volume roads.