intolerable for the societies. In our country, the number of car accident inpatients in year 2000 was reported 88.4 in 10000.3 Besides the harm and damages that accidents have for the individuals, there might be as well injuries and disabilities which can affect the fu- ture life of the individuals and reduce the quality of life. Accidents as well may have consequences in the economical life of the individuals. Most accidents cause unpredicted costs for the so- cieties while compensating these costs especially for the developing countries are difficult. In our country, the cost of car accidents is about 1 billion Dollars per year.3 This study aims at investigating the risk factors in the road accidents injuries around Mahshad City, Western Iran in 2007. Materials and Methods In a case-control study conducted from June to No- vember 2007, the cases were the drivers who drove on these roads and had a history of accident and the control group was the drivers driving in the same roads, having accidents but experiencing no damages or injuries. Most of the enquiries were performed at the place of accident or the emergency centers near the scenes. In the control group, the interview was performed as much as possible with the drivers and in the case group depending on the condition of the injured and level of consciousness, the interview was done with the drivers or ones accompanying him or her, in some cases the interview was postponed to the time that the injured driver became conscious later. The instrument for enquiry was questionnaire, the reliability and va- lidity of which were tested beforehand, the interview- ers had at least high school diploma and were trained to minimize the measurement errors at the time of investigation as much as possible. The effect of 12 independent variables was inves- tigated on the accidents. Variables under investigation were age, sex, seat belt, spontaneous combustion at the accident, trapping at the accident, falling out of the vehicle at the accident time, music playing in the vehicle at the time of the accident, using cell phone, the direction of the accident, the time, smoking at the time of the accident, and the model of the vehicle in both groups. The sampling was done based on the type of the study and to investigate the effect of use or not using a seat belt at the time of accident among the control Relative risk on car accidents and case groups. The sampling was based on the find- ings of the previous studies in which the probability was reported to be 1.53, with an error of 5% and power of 80%. In the case and control groups, 170 samples were enrolled. Based on the type of the study and the small sam- ple size, the sampling was done based on the objec- tive-based sampling procedure and the sampling con- tinued until the sampling population was achieved. In this study, all samples were selected from the Asian roads directing to Mashhad. The roads were Mashhad- Nayshabur, Mashhad-Torbat Heidariyeh, Mahshad- Taybaad and Mashhad-Ghuchan. It is worth mentioning that the design of this study exactly follows the design that Khalaji et al. used in their previous study.5 Our questionnaire and questions were also similar. The objective behind using the same instruments as khalaji et al. was to investigate the ef- fect of the variables under study, applying the same methodology as well helping the authors to draw con- clusions by means of comparing these studies. The data were analyzed by SPSS (Version 15, Chicago, IL, USA) and STATA software based on the objective of this study to investigate the risk fac- tors related to the drivers’ condition in the roads around Mashhad using logistic regression model. Af- ter indicating the risk factors in different logistic re- gression models, in order to find the ultimate risk fac- tors and separating them from the interrupters, a backward logistic regression was applied. In this model, in a multi-model based on the high- est non-significant p-value, the variables were omit- ted from the model and the ultimate model was based on the p-value less than 0.05 in a multi-model con- sisting of all remaining variables. Results Among the people who had the required characteris- tics of the study, 90% in the case group and 93% of the control group were willing or able to be inter- viewed. As Table 1 indicates, approximately 80% of the subjects (250 persons), were male and the 62 re- maining persons were female. The average age of the participants in this study was 37.4±10.3 years. The age range of the partici- pants was 18 to 69 years old and 16.2% of the case group and 23% of the control group were female. The distribution of males in both case and control groups was 83.8% and 76.6% respectively. Regression did WWW.ircmj.com Vol 13 August 2011 531