Lane Width ReallocationsBased on 5-Year Crash Data
Richard C. Moeur, PE
ADOT Traffic DesignMarch 2007 edition
Flagstaff
• Business Route 40 is primary east-west arterial street in Flagstaff
• Also known as “Route 66”• Was US 66 from 1920s-1980s• Currently signed as Historic US 66
• Currently owned & managed by ADOT• Will transfer to City of Flagstaff in future
Crash Analysis
• Part of design exception analysis for two B-40 paving projects in Flagstaff
• Looked at all reported crashes from MP 195 - 200• Jan 00 - Dec 04 (5 years)
• Bike-MV crashes make up nearly 25% of all reported crashes in corridor• (75 out of 300+ total crashes)
Bike-MV Crashes By Type
Bike-MV Crash Severity
Findings
• 60% of bicycle-motor vehicle crashes involved wrong-way bicyclists• 50% of crashes involved wrong-way
sidewalk or path riding
• 63% of bike-MV crashes involved sidewalk or path bicyclists
• 34% on north sidewalk BNSF OP - E Flg• 10% on south side path downtown - E Flg• 19% on other sidewalks (Milton, W 66)
Findings
• Only 1 crash involved an overtaking motorist colliding with a cyclist traveling in the roadway
• Motorist cited for 28-735
• Only 1 fatal crash• at B-40 onramp at East Flag TI
• Bicyclist at fault in 72% of crashes• Only 15% resulting in citation
Hot Spots
• 6 bicycle-MV crashes at Milton / B-40• 83% wrong way riding on sidewalk
• 6 bicycle-MV crashes at US 180 / B-40• 83% sidewalk riding
• 8 bicycle-MV crashes at Enterprise / B-40• 100% non-roadway cyclists
• 62% involving pathway users (south side)
• 75% involved wrong way riding
Critical Issues
• Wrong-way riding• Bicyclist approaches conflict points from
unseen and unexpected direction
• Sidewalk / path operation• Perceived as safer, but has higher crash risk• Bicyclists enter intersections unexpectedly
Sidewalk/Path Conflicts -Left Turn From Parallel Road
Sidewalk/Path Conflicts -Left Turn From Cross Road
Sidewalk/Path Conflicts -Right Turn From Cross Road
Critical Issues
• Low apparent percentage of bicyclists riding in roadway• Outside lane widths not sharable per 28-815
• Drivers must change lanes to pass• Bicyclists may be uncomfortable occupying lane• Relatively high traffic volumes
• Speeds consistent with urban arterial• apx. 40 MPH through much of corridor
Lane Widths
• AASHTO Green Book & ADOT Roadway Design Guide allow wide variety of lane widths
• 12 ft is ‘basic’ width• But is “worst-case” situation for sharing• Looks sharable, but really isn’t
• 10’ - 11’ are fully endorsed by AASHTO• 14’ is minimum sharable width
• ARS 28-735 requires 3 ft passing distance for bicyclists
Recommendations
• Discourage wrong-way riding
• Encourage on-street riding
Recommendations
• 60 ft roadway• (plus 2’ curb & gutter each side)
• Old lane widths• 2 x 12’ lanes each direction + 12’ TWLTL
• Revised lane widths• 10’ TWLTL• 11’ inside travel lanes• 14’ sharable outside travel lanes
Existing Lane Configuration
Recommended Lane Width Adjustments
ADOT Bike Policy
• ADOT will allow bike lanes or other facilities on state highways
• However, ADOT requires local agency responsibility for bike-specific signs & markings
• No agreement reached on B-40 (yet…?)
Possible Bike Lane or Shoulder Configuration
Questions?
• Presentation can be downloaded from:
• http://www.richardcmoeur.com/pres/b40flag.ppt