Guidance for Left-Turn Flashing Yellow Arrow (FYA) Implementation in Nebraska

Details

• Creators:
  Khattak, Aemal J. ; Zhao, Li ; Dzawu, Frank Selase
• Corporate Creators:
  Nebraska Transportation Center
• Corporate Contributors:
  Nebraska. Department of Transportation ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Crash Analysis Crashes Data Analysis Flashing Traffic Signals Implementation Left Turns Signalized Intersections Transportation Safety Yellow Change Interval
• Publication/ Report Number:
  SPR-FY24(037) ; 26-1121-3013-001
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Nebraska
• Edition:
  Final Report. February 2024-January 2026
• Corporate Publisher:
  Nebraska. Department of Transportation
• Abstract:
  This research evaluates the safety performance of flashing yellow arrows (FYA) and driver behavioral responses in Nebraska, using data from 324 FYA intersections (Lincoln 160; Omaha 164) to develop evidence-based implementation guidance. The study addresses critical knowledge gaps in local driver acceptance patterns, the effectiveness of phasing configurations, and a comprehensive safety assessment that integrates crash and conflict analyses. The methodology employed four complementary analyses: (1) negative binomial crash frequency modeling of 3945 unique left turn crashes(2015-2024) across Lincoln and Omaha; (2) binary logistic regression of 948 gap acceptance decisions across 43intersections; (3) linear regression of post-encroachment time for 613 completed left turns; and (4) detailed video investigation of 18 crashes at three Omaha intersections with lead-lag FYA phasing. Results demonstrate no statistically significant overall crash increase post-FYA installation when controlling for exposure (Lag: Incidence Rate Ratio [IRR]=0.937, p=0.364; Lead: IRR=1.027, p=0.563), though aggregate trends were influenced by five high-volume outlier intersections. Sensitivity analysis excluding outliers revealed lag phasing produced a statistically significant 15.1%reduction in crashes (IRR=0.849, p=0.038). Perceived Yellow Trap" (PYT) phenomenon, where lead-lag phasing configurations created perceptual confusion during phase transitions, accounting for 72% of observed crashes. Gap acceptance analysis showed lag phasing associated with 10% shorter critical gaps (3.85s vs. 4.28s), enabling higher operational efficiency. Recommended operational thresholds include prioritizing lag phasing at high-exposure locations, refining exposure thresholds using cross-product metrics, optimizing signal timing, and time-of-day operation. When properly implemented and following the recommended operational thresholds, FYA installation should improve intersection safety.
• Format:
  PDF
• Funding:
  SJ2324
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:625aa4762381f969ffaebffef34cf2a8316088153e4ed17bef81eb88e2c599f2966cbb6bcdc44453e8d3cd6d2e060e76e860e47a1c86ce2e4170d5a5d9526124
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/91137/dot_91137_DS1.pdf
• File Type:
  [PDF - 2.49 MB ]