Comparison of Calibration Methods for Improving the Transferability of Safety Performance Functions

Safety performance functions (SPFs) are critical for traffic safety management. They have been applied for identifying significant risk factors, estimating crash frequencies, and screening potentially hazardous locations. Since SPFs proposed by Highway Safety Manual (HSM) are developed based on certain states in the United States, regions without jurisdiction-specific SPFs need model calibrations for the localization of SPFs. The main objective of this study is to compare the typical calibration methods that used in the literature and identify the appropriate ones. Random effects Negative Binomial (NB) models were established for urban arterials in Shanghai and Guangzhou during peak hours and off-peak hours separately. Four calibration methods, including the calibration factor, empirical Bayes (EB) method, K Nearest Neighbor (KNN) regression method, and pooled data, were applied. The performance in improving model transferability was measured by transfer index and the adaptability to insufficient data was assessed by necessary data collected for each method. Based on the modeling results, pooled data approach that composed of the entire Shanghai dataset and 50% proportion of the Guangzhou dataset provides the best performance. And EB method and KNN regression method are preferable to the calibration factor. Furthermore, modeling and calibrating for different time periods should be considered when average speed is incorporated in the model.

• Supplemental Notes:
  • This paper was sponsored by TRB committee ANB25 Standing Committee on Highway Safety Performance.
• Corporate Authors:

  Transportation Research Board

  ,    
• Authors:
  • Wang, Xuesong
  • Tang, Dongjie
  • Pei, Saijun
• Conference:
  • Transportation Research Board 98th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2019-1-13 to 2019-1-17
• Date: 2019

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 8p

Subject/Index Terms

• TRT Terms: Calibration; Crash rates; Crash risk forecasting; Highway safety; Peak hour traffic; Risk assessment; Safety management; Traffic safety
• Identifier Terms: Safety Performance Functions
• Geographic Terms: Guangzhou (China); Shanghai (China)
• Subject Areas: Data and Information Technology; Highways; Safety and Human Factors;

Filing Info

• Accession Number: 01698344
• Record Type: Publication
• Report/Paper Numbers: 19-04352
• Files: TRIS, TRB, ATRI
• Created Date: Mar 1 2019 3:51PM