The Determination of Inconsistency Indicators in Rural Roads using Open-Source Geometric Data and Investigating Its Relationship with Accident Types
In general, the consistency of the geometric design measures the level of relationship between the driver's expectations and the behavior of the road geometry and it is an important factor in road accidents. Evaluation of road geometry by inconsistency indices requires road geometry information and an operating speed profile. Due to the lack of road geometric information in Iran, it is difficult to study this field. In this research, the method of obtaining road geometric information from street maps was first discussed, and then, based on this information and operating speed models, the speed profile was drawn for the road under study. After applying the segmentation methods, for each of them, the relationship between inconsistency indices and types of accidents has been investigated by safety performance functions with a Poisson or negative binomial model. The results showed that the inconsistency indices have a significant effect on overturning type accidents. In terms of significance level, Castello's inconsistency index, which is calculated using the inertial speed (for each point by weighting the operating speed in a certain period of time before that point) showed the best relationship with overturning accidents on two lane rural road. The development of inertial speed calculation methods and optimization of Castello's inconsistency index relationship with overturning accidents, showed that the value of the time interval before each point is 14 seconds and the value of alpha equal to 4.1 has the best performance in predicting overturning accidents.