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