Safety Effects of Flashing Yellow Arrow Update February 2009
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Transcript of Safety Effects of Flashing Yellow Arrow Update February 2009
Presentation Overview
• Background
• North Carolina Sites
• North Carolina Crash Data Monitoring
• Summary
North Carolina Installations
• Installations by year
Planned Installations
• 50+ sites: Design complete / installation pending• 50+ sites: FYA approved / Design in progress
North Carolina Crash Data Monitoring
• FHWA requirement that these sites are monitored • All sites monitored on a yearly basis (NEW!)
– Previously monitored quarterly• Due to number of sites now online, became inefficient to monitor
quarterly
– Some sites will be monitored more frequently as requested
• Currently monitoring 43 sites
Evaluation Challenges
• Relatively new device– Few sites– Little ‘after’ data
• Other changes made to signal at time of FYA installation– Timing changes, other signal head upgrades, turn lanes,
new developments, etc…– Difficult to single out effect of FYA
• Naïve before and after
PRELIMINARYBefore and After Crash Summary
Number of Sites: 3
Average Before Period: 2.1 years
Average After Period: 0.5 years
Grouped Before After Reductions
Category 1: Permissive Only to FYA Protected-Permitted
PRELIMINARYBefore and After Crash Summary
Grouped Before After Reductions
Significant Increase
Category 2: Protected Only to FYA Protected-Permitted
Number of Sites: 7
Average Before Period: 3.0 years
Average After Period: 0.8 years
PRELIMINARYBefore and After Crash Summary
Category 3: “Doghouse” Protected-Permitted to FYA Protected-Permitted
PRELIMINARYBefore and After Crash Summary
Grouped Before After Reductions
Category 3: “Doghouse” Protected-Permitted to FYA Protected-Permitted
Number of Sites: 13
Average Before Period: 3.0 years
Average After Period: 1.2 years
• Still not enough data to make conclusive safety statements
• Preliminary results seem promising• Likely will not see large crash reductions• Large increase in crashes at sites that
went from protected to FYA protected-permitted likely due to phasing change and not FYA itself
• TSU will continue to monitor and provide feedback
Key Points / Summary
Contact Information
Brian G. Murphy, PE(919) [email protected]
Traffic Safety Unit Website: http://
www.ncdot.org/doh/preconstruct/traffic/TSU/default.html