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Dr. Raghavan Srinivasan, HSRC

Low Cost Safety Improvements Pooled Funds Study Flashing Beacons at Stop Controlled Intersections Results. Dr. Raghavan Srinivasan, HSRC. Background on Strategy. Alert drivers to the presence of an intersection Reduce angle crashes

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Dr. Raghavan Srinivasan, HSRC

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  1. Low Cost Safety Improvements Pooled Funds StudyFlashing Beacons at Stop Controlled Intersections Results Dr. Raghavan Srinivasan, HSRC

  2. Background on Strategy • Alert drivers to the presence of an intersection • Reduce angle crashes • Initial installation costs: $2,000 to $ 100,000 • Placement Options • STOP Sign mounted • Overhead

  3. Literature Review • Previous Work • Cribbons and Walton 1970 • 14 rural sites • About 1 year before, 1 year after • Pant et al. 1999 • 6 sites without and 7 with a beacon • Murphy and Hummer 2007 • 34 locations in North Carolina • Empirical Bayes study - accounted for change in traffic volume using a linear assumption • Safety effectiveness has not been adequately quantified

  4. Objective • To examine the safety impact • Target crash types considered included: • Total intersection crashes. • Total intersection injury and fatal crashes (including fatality (K), Injury, incapacitating (A), Injury, non-capacitating (B), and possible injury (C). • Total intersection angle crashes. • Total intersection rear-end crashes.

  5. Objective • Determine if safety impacts are function of: • Area type (rural, suburban, or urban). • Intersection type (Two-way versus four- way stop-controlled). • Types of flashing beacon installations including standard and actuated. • Location of the beacon including stop sign or overhead.

  6. Study Design • Based on methodology suggested by Hauer (1997) • Literature review to determine the average number of crashes at stop controlled intersections • Sample size • Minimum: 53 intersection-years in the before period (ability to detect 20 percent reduction in crashes at 90 percent confidence level) • Desirable: 260 intersection-years in the before period (ability to detect 10 percent reduction in crashes at 90 percent confidence level)

  7. Data Collection

  8. Data Collection – North Carolina Total number of intersections used = 64

  9. Data Collection – South Carolina Total number of intersections used = 42

  10. Aggregate Evaluation Results: North Carolina

  11. Aggregate Evaluation Results: South Carolina

  12. Aggregate Evaluation Results: NC and SC Combined

  13. Disaggregate Evaluation Results: Angle Crashes

  14. Economic Analysis • FHWA cost per crash for unsignalized intersections (FHWA-HRT-05-051) • $13,238 for rear-end • $61,114 for right-angle • Economic Benefit • Based on combined results from NC and SC • $ 12,040 per site-year • Costs estimated for Standard and ‘Other’ types separately

  15. Economic Analysis • Standard Beacons: • $ 27,500 initial installation costs (high value) • Annual Maintenance and other costs: $ 720 • 10 year life • Annualized costs = $ 4,636 • Benefit Cost ratio is 2.6:1 • ‘Other’ Beacons: • Initial costs range from $ 5,000 to $ 100,000 • Benefit achieved if initial cost is less than $ 79,000 • 2:1 Benefit/Cost ratio if initial cost is less than $ 37,000

  16. Conclusions • NC: statistically significant reduction in total, angle, and injury and fatal crashes • SC: very little change • NC and SC combined: statistically significant reduction in angle and injury and fatal crashes • Probably more effective in rural and suburban locations

  17. Conclusions • Very few locations with stop sign mounted beacons • Standard beacons provide a benefit cost ratio of 2.6:1 • Net benefit of non-standard beacons depends on their cost

  18. Questions ???

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