1 / 13

SURROGATE SAFETY ASSESSMENT MODEL (SSAM) Prepared by: Joe Bared, FHWA

SURROGATE SAFETY ASSESSMENT MODEL (SSAM) Prepared by: Joe Bared, FHWA. Rear-end Conflict Lines. Conflict Lines. Conflict Points. Event Descriptions at Intersections. Intersection box. α. B. A. Calculate corresponding SSAM measures.

kimberly
Download Presentation

SURROGATE SAFETY ASSESSMENT MODEL (SSAM) Prepared by: Joe Bared, FHWA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SURROGATE SAFETY ASSESSMENT MODEL(SSAM)Prepared by: Joe Bared, FHWA

  2. Rear-end Conflict Lines Conflict Lines Conflict Points Event Descriptions at Intersections Intersection box

  3. α B A Calculate corresponding SSAM measures • Calculate the angle of the headings of the two vehicles and use this data to determine the conflict type: • if angleα >= 45 degree, then it is a crossing conflict; • If α <= 2 degree, then it is a rear-end conflict; • else, it is a lane change conflict. • Calculate the angle of the headings of the two vehicles and use this data to determine the conflict type: • if angleα > 85 degree, crossing conflict; • If α < 30 degree rear-endconflict; • else, it is a lane change conflict. Adding configurable angle thresholds in SSAM version 2

  4. Surrogate Measures • Minimum Time To Collision (TTC) • Minimum Post-Encroachment Time (PET) • Initial Deceleration Rate (DR) • Maximum speed (MaxS) • Maximum relative speed difference (DeltaS) • Location of the conflict event (CLSP, CLEP) • Maximum “post collision” DeltaV (MaxDeltaV)

  5. Conflict Point Diagram with Surrogates

  6. Comparison of Two Alternative designs

  7. Field Validation of 83 Signalized Intersections Relating crashes to conflicts

  8. Safety Ranking of Total Incidents • The Spearman rank-correlation coefficient between hourly conflicts frequency and annual crash frequency is a significant 0.46

  9. Safety Ranking Incident Type • The Spearman rank-correlation coefficient for rear-end conflicts/collisions is a significant 0.47 • The Spearman rank-correlation coefficient for sideswipe conflicts/collisions is a significant 0.47

  10. TTC <=0.5 s TTC <=1.0 s TTC <=1.5 s Conflicts: Case 1 High-speed conflicts for ten simulation runs - no crashes, conflicts at Vmax >= 10 ft/s Same as the previous slide, but with time-to-collision (TTC) composition CFI 609 total Conventional 573 total

  11. Conflicts: Case 1 T-Test: Significance of difference of CFI statistics from the conventional intersection statistics with 95% confidence interval, no crashes, conflicts of VMAX >= 10ft/s

More Related