safety and design national technical services team 1 systematic approach to intersection safety may...

Safety and Design National Technical Services Team

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Systematic Approach to Intersection

Safety

May 11, 2010

61st Annual Missouri Traffic and Safety Conference

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Why Intersection Safety?

A small part of overall highway system, but -

In 2008 – 7,772 fatalities related to intersections

(21% of Total Highway Fatalities)Each year more than 3.17 million intersection

crashes occur (over 55% of all reported crashes)

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2008 US National Total Crash Characteristics

Crash Type Total CrashesFatal/Injury

Crashes

Number % Number %

Non Intersection 2,638,000 45% 722,680 43%

Stop/No control Intersection

984,000 17% 321,520 19%

Signalized Intersection

1,182,000 20% 380,511 23%

Unclassified 1,005,000 17% 240,306 14%

Total 5,801,228 100% 1,637,476 100%Source: US DOT: Traffic Safety Facts 2008 Early Edition, A Compilation of motor vehicle crash data from FARS and GES, Table 29, Page 52

55% 57%

http://www-nrd.nhtsa.dot.gov/Pubs/811170.PDF


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2008 Traffic Fatalities (FARS)

US Missouri

Total Fatalities 37,261 960

Roadway

Departure

19,794

(53%)

616

Intersections 7,772

(21%)

162

(17%)

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The Goal of the Missouri Strategic Highway Safety Plan (SHSP) – Missouri’s Blueprint to Arrive Alive” is to reduce annual traffic fatalties to 850 by 2012. This is a 14.3% reduction from 992 fatalities that occurred in 2007. For Intersections, the goal is a reduction of 28 fatalites.

Missouri Focus State Intersection Safety Implementation Plan

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How the Intersection Safety Action Plan

was Developed – 2009:1. 6 years of intersection crash information compiled

and analyzed2. “Thresholds” were selected to identify those

intersections that produce 40%+ of the intersection crashes

3. Intersection Improvement Measures were selected by Category

4. Intersection Safety Implementation Plan Developed



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Locality Total CrashesTotal

Fatalities

Fatalities Per 100 Crashes

Total Disabling Injuries

Disabling Injuries Per 100 Crashes

State Roads

Rural 30,232 483 1.60 3,769 12.47

Urban 82,710 177 0.21 2,734 3.31

Total 112,942 660 0.58 6,503 5.76

Local Roads

Rural 10,154 53 0.52 531 5.23

Urban 139,491 164 0.12 3,275 2.35

Total 149,645 217 0.15 3,806 2.54

Table 3. Missouri Intersection Crashes, Disabling Injuries, and Fatalities for Stop-Controlled Intersections – 2002-2007

262,587


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Locality Total CrashesTotal

Fatalities

Fatalities Per 100 Crashes

Total Disabling Injuries

Disabling Injuries Per 100 Crashes

State Roads

Rural 4,107 17 0.41 227 5.53Urban 73,913 124 0.17 2,482 3.36Total 78,020 141 0.18 2,709 3.47Local Roads

Rural 676 5 0.74 11 1.63Urban 73,815 159 0.22 2,160 2.93Total 74,491 164 0.22 2,171 2.91

Table 2. Missouri Intersection Crashes, Disabling Injuries, and Fatalities for Signalized Intersections – 2002-2007


152,511

What Can the Intersection Safety Plan Do for Missouri?

more than 54,000 intersection crashes and 3,080 disabling injuries will be prevented along with at least 270 lives saved over a 10-year period once fully implemented



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Systematic Approach to Intersection Safety

Rather than focusing on only a few intersections with the highest number of crashes – “Top Down” (typical HSIP program) Systematic Approach focuses on the intersections with the majority of the crashes – “Bottom Up”


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Systematic Approach to Intersection Safety by the States:

Implementation Plans Identify those intersections that make up 40 to 60% of state total crashes Improve with low cost signing and marking and signal improvements: warning signs, double up, oversize, markings, Signal head per lane with backplates, etc. Break down the improvements into a series of annual elements over 5 years

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Developing and Implementing Intersection Safety Plans

South Carolina Louisiana Missouri Florida Indiana Mississippi Georgia Pennsylvania Ohio Massachusetts

Implementing the “Systematic Approach to Intersection Safety”

Approximately 40 percent of the fatalities occur on State rural highway system at Stop controlled intersections

1,108 intersections identified on state highways (rural and urban) for systematic improvement which have more than 6 crashes in 6 years (rural) or 50 crashes in 6 years (urban)


Over half of statewide intersection crashes and over ¼ of intersection fatalities occur at local urban intersections

236 intersections identified which have more than 6 crashes in 6 years (rural) or more than 50 crashes in 6 years (urban)



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Application of low cost counter measures: Signing and Marking and Minor Signal Visibility measures

- Rather than high cost geometric reconstruction of intersections


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Intersection Safety

Counter- measures


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Systematic Approach to Improving Intersection Safety

Warning

Guide

Regulatory Right-of-Way

The BASIC Elements are the two guiding principles of BEST Intersection Safety: Clarify and Simplify


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Warning

Guide




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Clarify and Simplify Example:

Warning

Signal Control of 2 rural State Highways


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Guide




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Guide




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Lane Use Signing - Overhead



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Signal Head per Lane

Supplemental Far Side Signal Head



Intersection Safety Countermeasures –

“Low Cost Safety Enhancements for

Stop-Controlled and Signalized Intersections” FHWA-SA-09-020


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“Low Cost Safety

Enhancements for Stop-

Controlled and Signalized

Intersections” FHWA-SA-09-

020

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Systematic Approach to Intersection Safety – 1. Signing

Warning

Guide



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Warning

Guide




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1.Warning

All-Way Stop of 2 rural State Highways


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2. Enhanced Warning



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Enhanced Advance Warning for Right-of-Way Controls - “Doubling-Up”

Lexington County, SC


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Enhanced Advance Warning Signing for Right-of-Way Controls – “Doubling Up”

Doubled-Up Stop Aheads


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3. Enhanced Warning



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STOP AHEAD Pavement

Markings 3. Enhanced Warning


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4. Guide



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5. Regulatory Right-of-Way

Stop Sign on outside of large right turn radius is too far out of center attention window of driver



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4-38


Add Stop Sign on Island to Enhance Visibility CMF = 0.89+ Right Hand Supplementary Stop Sign All-Way Stop

of 2 rural State Highways


Right-of-Way Control Signing –B. Visibility

(Relocate Stop to Improve Visibility)


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Visibility (Supplemental Stop Sign in Island)

*NCHRP 500, Strategy 17.1 E3 – Install Splitter Islands on Minor Road Approaches


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Emphasis Treatment: Increase Size

Oversized STOP Signs

*NCHRP 500, Objective 17.1 E5 – Install larger regulatory signs


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“Double Up” Stop Signs


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7. STOP Beacon



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Sight Obstruction

Systematic Approach to Intersection Safety – 2. Improve Sight Distance

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Sight Obstruction


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Move Stop Bar Forward


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Move Stop Bar Forward


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- Move Stop Bars Forward


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-Installation of lighting of rural intersections reduced crashes by 25 to 50% (MN study)- CMF = 0.70 (Elvik & Vaa)- unlighted rural intersection had twice the number of crashes vs. lighted intersections (Iowa CTRE 2008 study) - CRF = 0.65 FHWA-SA-09-017

NCHRP 500, Strategy 17.1 E2-Improve Visibility of Intersection by Providing Lighting (P)

Systematic Approach to Intersection Safety – 3. Intersection Lighting

Systematic Approach to Intersection Safety – 3. Intersection Lighting

-Iowa CTRE study of 232 rural unsignalized Intersections found the night to day crash ratio for lighted intersections was 0.39 vs. 0.61 for unlighted intersections

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CRF = 35% right angle crashes

4 heads for 4 lanes 1 head for 1 Rt lane

1 head for 1 Lt lane

*NCHRP 500, Strategy 17.2 D2: Improve Visibility of Signals

CRF = 28% total crashes


– 4. Signal Visibility:

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2 heads for 2 lanes 1 head for 1 Rt lane

2 head for 2 Lt lanes

*NCHRP 500, Strategy 17.2 D2: Improve Visibility of Signals

CRF = 28% total crashes




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4 approach lanes4 signal heads

- Place Primary Signal Heads over each Through lane



Jackson, MS


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Add Back Plates

CRF = 13% total crashesCRF = 50% right angle crashes

No Back Plates Back Plates




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Right Hand Curve

Supplemental Signal on span wire



Add Supplemental Signal Head(s)


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1. Update Yellow Clearance IntervalAll-Red TimeYellow Time

*NCHRP 500, Objective 17.2 A2 – Optimize Clearance Intervals

NY study:CRF =8% total crashesCRF = 12% injury crashesCRF = 39% ped crashes

NY study:9% decrease in multi-vehicle crashes


–5. Signal Clearance Intervals:


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CRF = 12% to 38% of total crashes – 3 studies


*NCHRP 500, Objective 17.2 A4 – Employ Signal Coordination


– 6. Signal Coordination:


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Ohio – 90th Worst Intersection for State – 184 crashes in 3 years


–Signal Example:


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Apply two guiding principles for design and operation of an intersection: Clarify Simplify

Identify Underlying Crash Cause:AIRS Crash Data identified 85% of Crashes were Red Light Running


Signal Example:


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Removed 7 signs including 2 overhead guide signs from overpass Signal Heads Positioned over Lanes into Driver’s Line of Sight Lowered signal heads on Mast Arms Added Supplemental Left Hand Signal Added Back Plates to Signal Heads Removed two street light poles


Signal Example:


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4 month Period Before – 15 Crashes 12 month Period After - 7 Crashes


Signal Example:

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Systematic Approach to Intersection Safety by the States:

Implementation Plans 12 states have developed Implementation Plans for Systematic Approach to Intersection Safety todate 7 states are actively reviewing the identified intersections and conducting engineering field reviews. 7 states have revised their engineering standards to provide for enhanced low cost signing and marking and for signal head per lane with back plates 3 states have let contracts for the first year annual element for systematic improvement


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Systematic Approach to Intersection Safety – Results:

South Carolina: A Before (3 years of crash data) and After Study (3 years of crash data) was performed on the first 91 locations improved in 2003. Crash Rate Reduction of 54.7% Severity Index Reduction of 54.5% A Injury percentage reduction of 34.8% A Fatality percentage reduction of 75% Average Benefit/Cost ratio was 385.


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Questions and Discussion:

safety and design national technical services team 1 systematic approach to intersection safety may...

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