| Transportation Engineering |
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| Application of generalized estimating equations for crash frequency modeling with temporal correlation |
| Wen-qing Wu, Wei Wang, Zhi-bin Li, Pan Liu, Yong Wang |
| Jiangsu Key Laboratory of Urban Intelligent Transportation Systems, Southeast University, Nanjing 210096, China; Jiangsu Province Collaborative Innovation Center of Modern Urban Traffic Technologies, Nanjing 210096, China; School of Transportation, Southeast University, Nanjing 210096, China; School of Management, Chongqing Jiaotong University, Chongqing 400074, China |
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Abstract Traditional crash frequency modeling uses crash frequency data averaged across multiple years. When data size is small, crash data in each year are used in the modeling to extend the size of the samples. The extension of sample size could create a temporal correlation among crash frequencies of the different years, which could affect the modeling accuracy. The primary objective of this study is to evaluate the application of the generalized estimating equation (GEE) procedures to account for the temporal correlation in the longitudinal crash frequency data. Four-year crash data at exit ramps on a freeway in China were collected for modeling. Based on the same data, traditional generalized linear models (GLMs) were estimated for model comparison. Results showed that traditional GLM underestimated the standard errors of coefficients for explanatory variables. The GEE procedure with an exchangeable correlation structure successively captured the temporal correlation among the crash frequencies of the different years. The GLM with GEE outperformed the traditional GLM in providing a good fit for the crash frequency data. Results of this study can help researchers better understand how various factors affect the crash frequencies at freeway divergent areas and propose effective countermeasures.
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Received: 22 October 2013
Published: 08 July 2014
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