Abstract
Crash prediction of the sharp horizontal curve segment of freeway is a key method in analyzing safety situation of freeway horizontal alignment. The target of this paper is to improve predicting accuracy after considering the elastic influence of explanatory variables and interaction of explanatory variables on crash rate prediction. In the paper, flexibility and elasticity are defined to express the elastic influence of explanatory variables and interaction of explanatory variables on crash rate prediction. Thus, we proposed 6 types of models to predict crash frequency. These 6 types of models include 2 NB models (models 1 and 2), 2 GNB models (models 3 and 4), one NB model (model 5), and one GNB model (model 6) with flexibility and variable elasticity considered. The alignment and crash report data of 88 sharp horizontal curve segments from different institutions were surveyed to build the crash models. Traffic volume, highway horizontal radius, and curve length have been assigned as explanatory variables. Subsequently, statistical analysis is performed to determine the model parameters and conducted sensitivity analysis by AIC, BIC, and Pseudo R2. The results demonstrated the effective use of flexibility and elasticity in analyzing explanatory variables and in predicting freeway sharp horizontal curve segments. In six models, the result of model 6 is much better than those of the other models by fitting rules. We also compared the actual results from crashes of 88 sharp horizontal curve segments with those predicted by models 1, 3, and 6. Results demonstrate that model 6 is much more reasonable than the others.
Highlights
Accidents, and highway-vehicle accidents, cost the lives of roughly one and a quarter million people worldwide every year
A wide variety of advanced statistical count models are applied to crash frequency analysis over the past years, and the strengths and weaknesses were well summarized by Lord and Mannering [5], Mannering and Bhat [12], and Mannering et al [13]
Flexibility and elasticity are defined to express the elastic influence of explanatory variables and interaction of explanatory variables on crash rate
Summary
Highway-vehicle accidents, cost the lives of roughly one and a quarter million people worldwide every year. Improved NB and GNB models were successfully used to predict the crash rate of freeway basic segment, tunnel entrance and exit, and so on [10, 11]. Most of these models with fixed parameters fail to reveal the true interrelationship between explanatory variables. Since we have discussed the crash prediction model of the basic segments in the paper published in Journal of Southeast University (Wang et al 2014), we take the freeway sharp horizontal curve segment (SHCS) as the research object in this paper.
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