A Disaggregate Speed Consistency Measure for Safety Evaluation of Freeway Diverging Areas

The most commonly used aggregate speed consistency measures (e.g. ΔV85) have ecological fallacy problem and overestimate safety performance. To weaken these pitfalls, this paper presents a disaggregate measure, the 85th percentile individual speed difference 85(ΔV), to assess the safety performance of freeway diverging areas. A diverging area is divided into four elements, namely the upstream mainline, diverging area, downstream mainline and exit ramp. Individual speeds at the four elements of each site are shot using radar guns. The last three digits are recorded for tracing individual vehicles. More than 30,000 traceable individual speeds, together with geometric and volume information, are collected at 21 diverging areas along the freeway G42 and G2501 in Nanjing, China. The evaluation results indicate that ΔV85 is overestimation-prone, which may lead decision-makers to leave potential unsafe sites unattended. The ratio of 85(ΔV)/ΔV85 varies from site to site and linkage to linkage, ranging from 1.1 to 4.6. The difference between ΔV85 and 85(ΔV) magnifies when the traffic conditions become diverse and complicated. The findings in this paper show that the disaggregate measure is more reasonable and persuasive in safety evaluation.

• Record URL:
  • http://onlinepubs.trb.org/onlinepubs/conferences/2011/RSS/2/Guo,T.pdf
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• Supplemental Notes:
  • Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
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  Transportation Research Board

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• Authors:
  • Guo, Tangyi
  • Liu, Yingshun
  • Deng, Wei
• Conference:
  • 3rd International Conference on Road Safety and Simulation
  • Location: Indianapolis Indiana, United States
  • Date: 2011-9-14 to 2011-9-16
• Publication Date: 2011

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 14p
• Monograph Title: 3rd International Conference on Road Safety and Simulation

Subject/Index Terms

• TRT Terms: Diverging traffic; Freeways; Highway safety; Off ramps; Speed; Traffic estimation; Traffic simulation; Traffic volume
• Geographic Terms: Nanjing (China)
• Subject Areas: Highways; Safety and Human Factors; I82: Accidents and Transport Infrastructure;

Filing Info

• Accession Number: 01504280
• Record Type: Publication
• Files: TRIS, TRB, ATRI
• Created Date: Jan 24 2014 2:29PM