How did the Bicyclist Cross the

Road?  

By: Mike Hendrix, PE, PTOE Date: June 26, 2012

A Case Study of Two

Intersections in Seattle 

 

Seattle Bike Master Plan

A blueprint for making improvements to Seattle’s bicycle network

Adopted in 2007

Seattle BMP Goals:

Triple bicycling by 2017 Reduce bicycle collisions by 1/3

between 2007 and 2017

Seattle Bike Master Plan

Seattle BMP Accomplishments:

Installed 129 miles of on-street facilities including bike lanes and sharrows

Added over 9 new miles of multi-use trail improvements

Implemented 98 miles of signed bicycle routes

Installed over 2,200 bicycle parking spaces

Case Study

What? Analysis of 2 intersections before and after

signal installation Both intersections were along a neighborhood

greenway Signals weren’t warranted based on MUTCD

criteria

Why? To determine if the traffic signals

installed along this neighborhood greenway improved conditions – for ALL users

Case Study

Determined changes in volumes

Determined changes in collisions

Observed operational issues

Background

Unwarranted signals are BAD. They:

Increase collisions Increase red-light running Increase delay Increase noise and air pollution Lead to increased maintenance costs Lead to a potential increase in cut-

through traffic

Background

2011 Pinellas County Study:273% annual increase in collisions 2008 Kentucky Study:28.3% increase in collisions221.7% increase in rear-end collisions 1989 New York City Study:65% increase in collisions 1979 Purdue University Study3,200 to 4,200 vehicle hours of delay

General Site Conditions

Site 1Fremont Ave N & N 80th St

Fremont Ave N – 25’ wide residential street

N 80th St – 1 lane each direction with on-street parking on north side

15,500 vpd (N 80th St)

700 vpd (Fremont Ave N)

Signal turn-on 11/16/2007

Site 2Fremont Ave N & N 105th St

Fremont Ave N – 25’ wide residential street

N 105th St – 2 lanes each direction with no on-street parking

23,000 vpd (N 105th St)

900 vpd (Fremont Ave N)

Signal Turn on 10/7/2010

Signing and Markings

Span Wire Sign Pavement Marking

Pre-Signal Conditions

Pre-Signal Warrant Summary

At N 80th Street At N 105th Street

Signal Warrants Not Met Not Met

PHB Warrants Not Met Met

Caltrans Bike Warrant Not Met Not Met

Fremont & N 80th StBefore Collision History

3 Years BeforeCorrectable Crashes 11

Non-Correctable Crashes 2

Crash Rate (Crashes per MEV) 0.751

Severity Index 1.77

Fremont & N 105th StBefore Collision History

3 Years BeforeCorrectable Crashes 3

Non-Correctable Crashes 5

Crash Rate (Crashes per MEV) 0.314

Severity Index 1.25

Delay

Intersection

Pedestrian Delay

(seconds)

Motor Vehicle Side Street

Delay (seconds)

Bikes as Motor Vehicles Side Street Delay

(seconds)Bikes as

Pedestrians Side Street

Delay (seconds)

NB SB NB SB

Fremont Ave N & N 80th St 237.2 32.5 27.2 Not Available 52.2

Fremont Ave N & N 105th St 5,297.9 44.8 53.4 124.5 109.4 247.0

Post-Signal Conditions

Post-Signal Warrant Summary

At N 80th Street At N 105th Street

Signal Warrants Not Met Not Met

PHB Warrants Met Met

Caltrans Bike Warrant Not Met Met

Fremont Ave N & N 80th StAfter Collision History

3 Years Before 3 Years AfterCorrectable Crashes 11 0

Non-Correctable Crashes 2 3

Crash Rate (Crashes per MEV) 0.751 0.200

Severity Index 1.77 1.00

Fremont Ave N & N 105th StAfter Collision History

3 Years Before 1 Year AfterCorrectable Crashes 3 0

Non-Correctable Crashes 5 1

Crash Rate (Crashes per MEV) 0.314 0.122

Severity Index 1.25 1.00

Volume Changes

IntersectionBicyclists Pedestrians Motor Vehicles

Before After Before After Before AfterFremont Ave N & N 80th St N/A 14 2 17 72 69

Fremont Ave N & N 105th St 21 52 10 20 77 85

Operational Issue: Violations

Fremont Ave N & N 80th St NB: 12.8% (23 cars) SB: 14.1% (22 cars)

Fremont Ave N & N 105th St NB: 13.5% (38 cars) SB: 12.9% (30 cars)

Operational Issue: Hot Spot Marking

Fremont Ave N & N 105th St

27 of 232 (11.6%) bicyclists went directly for pedestrian push button.

Fremont Ave N & N 80th St

Roughly same proportion

Summary

Neither signal met 2009 MUTCD signal warrants. Both met PHB warrants in the after condition.

Collisions and collision rates decreased at both signals following signal installation.

Severity of collisions at both signals decreased following the signal installation.

Summary

Bike and pedestrian volumes increased while motor vehicle volumes remained relatively constant.

Significant portion of motorists observed violating turning restrictions.

Observed significant misunderstanding of “Hot Spot” markings by bicyclists.

Thank you for your time!

Questions?

Contact InformationMike Hendrix, PE, PTOEmhendrix@perteet.com206-436-0515