INTODUCTION: Human factor is identified as the most important factor in road accidents. The purpose of this research was to compare the role of human factor in road accidents in different drivers' categories in Darab Township in 2010.
METHODS: In this descriptive-correlation research, firstly, four groups of drivers including bus, truck, taxi and private car drivers (130 drivers) were selected through purposeful sampling and completed Manchester Driving Behavior Questionnaire (MDBQ). Data was analyzed by using Multivariate Analysis Of Variance (MANOVA), correlation coefficients and SPSS.
FINDINGS: According to the results, all groups had significant differences in all factors such as errors, lapses, aggressive and ordinary violation (P<0.05); also the highest rate in 3 factors of errors, lapses and aggressive violation were related to bus drivers, truck drivers, private car drivers and taxi drivers respectively; but in ordinary violations the highest scores were related to private car, taxi, truck and bus drivers respectively. The findings of correlation coefficients were as follows: there were a significant and positive correlation between age and all types of errors and violence (P<0.05); negative and significant correlation was found between education with dangerous and aggressive errors and lapses (P<0.05); but positive and significant correlation was found between education and aggressive violation (P<0.05); there was no correlation between education score and ordinary violation; also, no correlation was found between years of driving and wearing safety belt with errors and violence (P>0.05).
CONCLUSION: The results indicated that the highest scores were specially related to bus drivers and truck drivers. Therefore, it is recommended to perform psychological assessments and adequate training in order to reduce the accident rate at the time of selection and obtaining driving licenses and periodically thereafter.

Background: Today, accidents and damages caused by road transport are one of the major problems in the country. The performed analyses on the factors affecting road accidents have shown that the human factor plays the biggest role in accidents. Therefore, this study examined human factors and classified them from drivers’ viewpoint; also offered the effect of each factor with analytical approach. Methods: In this cross-functional study, all affected drivers (217 persons) in Piranshahr- Sardasht road were examined by Cochran formula using self-administrated questionnaire in 2012-2013. Also, the validity and reliability were calculated by using cronbach’s alpha. In order to analyze data, the parameters of frequency, mean, standard deviation and linear regression were used. Findings: The relationship between each of biological aspects with the extent and severity of road accidents were calculated and confirmed ba sed on the regression coefficient such as deficits in cognitive, motor, and sensory perception relative to individuals, diseases and disabilities and aging, personal and psychological factors such as drug and alcohol abuse, high speed, drowsiness, overtaking, ignoring the warning signs, long driving without rest, closing seatbelts, having experience and previous accident, lack of confidence in driving, stress and lack of accurate vehicle inspection, short-term capabilities such as overeating, smoking, using cell phone or even talking to passengers. These factors classified are known as "risky driving behavior" and included any type of behavior that increases the risk of accident or injury following the accident. Conclusion: According to the results, human factors related to traffic accidents on the road are in two general groups which related to human neurobiological performance and out of driver’s control and management; also, factors related to the field of personality act together in complex interaction. The findings showed that several factors such as biological aspects, personal and psychological factors, and short-term capabilities can be seen in one person which influence on incidence and severity of road accidents