Dr. Raghavan Srinivasan, HSRC

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 ???