Vafaee-Najar et al. model and were correlated with the amount and se- verity of the injuries. But since falling out of the car was significantly higher in cases not using seat belts, this variable was omitted from the model and the trapping was omitted with it as well. Discussion This study is a case-Control study which aims at in- vestigating the danger factors of accidents occurring in the roads around Mashhad, in year 2007. The se- lection of the control in case-control studies is always considered as an important variable, in this study alt- hough the control group was selected from the drivers having accidents in the same roads but due to some demographic variables, there were some measurement errors which were considered as the limitations of this study, which may influence the accuracy of the study too. Another factor in this study was the critical con- ditions of the case group which made them unable or unwilling to be interviewed; therefore some severe cases were automatically omitted from our study. But still since we were able to study at least 90% of the cases in both groups, this error was minimized. An- other limitation of our study was that we could not get honest and clear answers about the possibility of using drugs, which may act as interference and affect some relations in positive or negative way. Due to the mentioned limitations and small number of popula- tion, care must be given while comparing the results of the study with other cases. The severity of the accidents is also considered as an important factor, the studies in this regard indicate that this factor may influence other variables. This factor is highly correlated with pace and weight of the vehicle, even though it is important to remember that we have study.5 For instance, injures, combustion and trapping and some other variables may correlate with the severity effect, therefore it is important to consider this variable. In order to facilitate the comparison, our results have been presented with Khalaji et al.’s results in Table 4.5 Several studies have been conducted in this regard all around the world, but due to differences in life style, roads condition, and other related factors the comparison may not be considered as accurate. Among the studies conducted so far, khalaji et al.’s study which considered Qazvin-Lushan road in year 2005 with the same methodology seems to be a pro- found and proper case for comparison.5 It is also worth mentioning that most studies in this regard in our country have been descriptive, so testing hypoth- esis with analytical studies may contribute a lot to the existing knowledge and conclusions.6-13 It seems that sex can be deemed as an important var- iable to begin comparison within such studies, as this study also indicated that sex did not have a significant effect on the accidents in both case and control groups. Although the amount of accidents was higher in men,12 but most studies indicated that, the severity of accidents was similar in both groups.5,14 Some studies have indi- cated the more severity of accidents in men.15 The average age of the case group is reported 5 years less than the control group; most studies indi- cate that lower age of driver were correlated with the severity of the accidents.15 Of course, some other studies such as Khalaji et al. and Norris et al. have rejected the correlation of the age factor with the se- verity of the accidents.5,14 Khalaji et al.’s study indi- cates that 42.8% of the case and 57.2% of the control group used protective tools such as seat belt.5 In the present study, the fastening of seat belt in the case group was reported as 42.9% and in control group 62.7%, this shows that our result were correlated with Table 4: Comparing this study with Khalaji et al.’s study. Variable Our study Case% Fastening seat belt 9.42 Being thrown out of the car 29.2 Car Model 55.2 Combustion 20.9 Direction of Contact Behind 24.7 Front 54.5 Next 20.8 Control% 62.7 5.7 51.3 1.3 42.4 30.4 27.2 Khalaji et al.’s study Case% Control% 42.8 57.2 26.9 5.1 53.1 50.9 6.3 0 12 16 46.3 36 41.2 47.9 not focused on the severity of the accidents, and it may only be considered as an interrupting variable in our khalaji et al.’s results supporting the positive role of seat belt in reducing accident’s severity.5 534 WWW.ircmj.com Vol 13 August 2011