U.S. Department of Transportation
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This report is an archived publication and may contain dated technical, contact, and link information |
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Publication Number: FHWA-HRT-11-024
Date: April 2011 |
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Safety Evaluation of the Safety Edge TreatmentPDF Version (1.29 MB)
PDF files can be viewed with the Acrobat® Reader® FOREWORDAdvancing the safety of America’s highways is a top priority for the Federal Highway Administration (FHWA). Through roadway design, cost-effective countermeasures, and advanced analytical practices, the FHWA Office of Safety Research and Development supports this objective by encouraging the development and implementation of improvements, such as the safety edge, that exhibit real safety benefits for the driving public. This study evaluated the safety effectiveness of the safety edge treatment in conjunction with resurfacing, a cost-effective safety improvement that can reduce crashes and fatalities. Development of the safety edge treatment was based on a need to reduce drop-off-related crashes and on engineering judgment. The evaluation utilized a before-after empirical Bayes analysis for determining a crash reduction factor for this roadway treatment. Furthermore, the study conducted a benefit-cost analysis to determine the advantages of applying this treatment to rural highways. This analysis of the safety edge highlights the benefits of a low-cost improvement through improved roadway design and evaluation. This report will interest safety and highway agency engineers who have a shared responsibility for public safety and an interest in implementing low-cost roadway safety treatments. Monique R. Evans NoticeThis document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document. Quality Assurance StatementThe Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. Technical Report Documentation Page
SI* (Modern Metric) Conversion Factors Table of ContentsChapter 1. Background and Research Objectives
Chapter 3. Preliminary Analysis Results for Field Measurements of Pavement-Edge Drop-Offs
Chapter 4. Analysis Results for Safety Evaluation Chapter 5. Estimated Cost of the Safety Edge Treatment
Chapter 6. Benefit-Cost Analysis
Appendix A. Identification of Drop-Off-Related Crashes Appendix B. Pavement-Edge Drop-Off Data Collection Methodology
Appendix C. Scatter Plots of Accidents and AADT List of figuresFigure 1. Diagram. Safety edge detail Figure 3. Graph. Comparison of Georgia SPFs by crash severity and roadway and shoulder type Figure 4. Graph. Comparison of Indiana SPFs by crash severity and roadway and shoulder type Figure 5. Diagram. Typical cross section for the safety edge treatment on one side of the road Figure 6. Graph. Minimum benefit-cost ratios for the safety edge treatment as a function of AADT Figure 7. Graph. Maximum benefit-cost ratios for the safety edge treatment as a function of AADT Figure 8. Illustration. Sample data collection form Figure 9. Illustration. Data collection intervals Figure 10. Illustration. Measurement of drop-off perpendicular to pavement surface Figure 11. Photo. Measurement of pavement-edge drop-off height Figure 12. Graph. Georgia multilane roadway with paved shoulder Figure 13. Graph. Georgia two-lane roadway with paved shoulder Figure 14. Graph. Georgia two-lane roadway with unpaved shoulder Figure 15. Graph. Indiana two-lane roadway with paved shoulder Figure 16. Graph. Indiana two-lane roadway with unpaved shoulder List of tablesTable 1. Summary of number and total length of sites Table 2. Summary of total non-intersection crash data for study sites Table 3. Summary of fatal and injury non-intersection crash data for study sites Table 4. Summary of traffic volume data for study sites Table 5. Summary of lane widths for study sites Table 7. Summary of pavement-edge drop-off height measurements Table 10. SPFs for Georgia sites Table 11. SPFs for Indiana sites Table 12. Run-off-road and drop-off-related crash frequencies as a proportion of total crashes Table 13. Georgia SPF calibration factors Table 14. Indiana SPF calibration factors Table 17. Before-after EB evaluation results for total crashes Table 18. Before-after EB evaluation results for fatal and injury crashes Table 19. Before-after EB evaluation results for PDO crashes Table 20. Before-after EB evaluation results for total run-off-road crashes Table 21. Before-after EB evaluation results for fatal and injury run-off-road crashes Table 22. Before-after EB evaluation results for PDO run-off-road crashes Table 23. Before-after EB evaluation results for total drop-off-related crashes Table 24. Before-after EB evaluation results for fatal and injury drop-off-related crashes Table 25. Before-after EB evaluation results for PDO drop-off-related crashes Table 27. Cross-sectional analysis of safety edge treatment effect for the period after resurfacing Table 28. Comparison of proportions of fatal and injury crashes before and after resurfacing Table 29. Summary of Georgia resurfacing project costs (2005) Table 30. Summary of Indiana resurfacing project costs (2005) Table 31. Summary of New York resurfacing project costs (2005) Table 32. Summary of combined Georgia, Indiana, and New York resurfacing project costs (2005) |