## 5 Discussion  
A speed range-based fine system was introduced after the installation of speed monitoring cameras. A 10 km/h buffer speed was allowed over and above a given speed limit as per this system. For instance, no fines up to 130 km/h on a highway segment with a 120 km/h speed limit. The fines start at speeds higher than the buffer speed but less than 20 km/h. The fine amount doubles or more for over-speeding by 20 km/h to 30 km/h, and so on. Figure 7 describes an evident accident risk reduction after the installation of speed camera. This road safety improvement strategy has eliminated the hot spots on the Buraydah Ring Road with no segment with a medium or higher risk index. The results show that such type of countermeasure worked successfully, as the drivers' behavior changed.  
The results presented in Figure 7 demonstrate the direct benefits of speed cameras on major highways in terms of risk reduction. Table 5 presents the data obtained for other main highways in Qassim Region. The data shows a more than 50% reduction in a total number of accidents and a 33% to 100% decline in fatalities. It is worth to mention that the stated percent reduction in traffic accidents as well as associated fatalities may be partly due to regression-to-mean (RTM) phenomenon in addition to those resulted from countermeasures (cameras) installation. According to RTM traffic accidents follows natural short-term fluctuations around expected/mean accidents frequencies. Thus, it is statistically possible that a period of high accident frequencies will be followed by low accident frequencies even in the absence of mitigation interventions and vice versa. For this study, the percent reduction in both accident frequencies and fatalities was significantly high that may not be solely attributed to RTM phenomenon, which implies that speed cameras were effective in improving the highway safety in the study area.  
Although significant improvements have been achieved with the installation of speed cameras in the study area, a rapid increase in traffic volumes is expected in the future. With this increase, additional road safety measures would be required. It can be seen in Figure 6 that the segments connected to major collectors and distributors of the Buraydah City suffered through higher accident risk prior to speed cameras installation. These approaches need to be carefully analyzed for additional safety measures. Heavy traffic is common on major highways of the Qassim Region due to the extensive inter and intra-regional agricultural trade. Past studies on traffic safety in Saudi Arabia have identified the significant factors (road, driver, and environmental) contributing to road accidents. Geometrics of merging and diverging lanes, traffic control, and traffic calming steps need to be carefully evaluated for their site-specific implementations in the Qassim Region. The accident risk assessment methodology developed in the present study can be implemented  
Figure 7: Percentages of the road segments with risk levels: (**a**) before installation of speed cameras; (**b**) after installation of speed cameras.  
on the Highways given in Table 5 and other major urban or rural highways in Saudi Arabia for hotspot identification and appropriate positioning of speed cameras.