Safety Effects of Flashing Yellow Arrow Update February 2009

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

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

Grouped Before and After Data

PRELIMINARYBefore and After Crash Summary

Category 1: Permissive Only to FYA Protected-Permitted

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

Category 2: Protected 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

PRELIMINARYBefore and After Crash Summary

All Categories Summarized

• 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