Transcript Using Quantitative Safety Measures to Inform Design

HSM: Celebrating 5 Years Together
Brian Ray, PE
Casey Bergh, PE
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HSM Promotes Quantitative Safety Methods
20
Crashes
16
12
8
4
0
0
2
4
6
8
10
Years
Crashes
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Expected Average
12
14
16
HSM Promotes Quantitative Safety Methods
Source: NCHRP 480
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HSM: A Multipurpose Toolbox
• Planning, design, construction, operation, and maintenance
• System Planning
– HSM Part B
• Project Planning & Preliminary Engineering
– HSM Part B and Part C
• Design and Construction
– HSM Part C and Part D
• Operations and Maintenance
– HSM Part B, C and D
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Part B - Roadway Safety Management
• Develop
understanding of
system needs
• Inform
countermeasure
selection
• Prioritize projects
with potential for
crash reduction
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Part B Performance Measures
• Multiple performance
measures available
– Simple to rigorous
– Data has limited most
agencies
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Part C – Predictive Method
x
 (C MF1x C MF2x  ...C MFyx ) C x
• SPFs predict crashes for
a base condition
• Part C CMFs modify the
base prediction to
reflect physical
conditions (e.g., leftturn lanes)
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16
Crashes Per Year
N predicted  N spf
Safety Performance Function
(SPF)
12
8
4
0
5000 10000 15000 20000 25000
AADT
Part D - Crash Modification Factors
• Provided in Part D and online in FHWA Clearinghouse
• Estimate change in crash frequency associated with a
proposed modification
Location - Improvement
Anderson Road Int. - FHWA Lane
Narrowing
Anderson Road Int. - FHWA Splitter
Island
Moon Road- Access Restriction /
Right Turn Lane
Anderson Road- Single Lane
Roundabout
Expected
Crashes/Yr
Estimated
Percent
Reduction
Planning
Level Cost
Estimate
$/Crash
Mitigated Over
Design Life
2.2
31%
$45,000
$13,196
2.2
68%
$112,500
$15,040
1.9
26%
$610,000
$61,741
2.2
71%
$3.15 million
$100,832
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HSM Applications in OR
State/Region
City/County
Intersection/
Segment
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• ODOT Pedestrian
and Bike Safety Plan
• ODOT ARTS
• TSPs
• Clark County
• Bend
• Clackamas County
• Road Safety Audits
• Intersection Traffic Control Evaluations
• US 97 Corridor Safety Study
State/Region Network Screening Identifies Sites with
Potential for Crash Reduction
• Segment screening based on sliding window
Segment #6
Segment #5
Segment #4
Segment #3
Segment #2
Segment #1
Milepost:
0
0.2
0.4
0.6
0.8
• ODOT ARTS systemic safety network screening focus
areas
– Roadway Departure
– Bicycle and Pedestrian
– Intersection
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1.0
ODOT Region 1 ARTS: Data-informed 300% Systemic
Project Locations
• HSM Performance Measure: Equivalent Property
Damage Only (EPDO) average crash frequency
– Selected to reflect the severity of reported crashes
• Applied independently to intersections and segments
– Weighting Factors (consistent with SPIS):
• 100 for Fatal or Injury A
• 10 for Injury B or C
• 1 for PDO
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Region 1: Data-informed 300% Systemic Project
Locations
• Traditional Systemic Analysis
– Use crash history to prioritize intersection crash locations
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Statewide Pedestrian and Bicycle Safety
Implementation Plan
• Risk-based Systemic Safety Analysis
– Crash history is not sufficient to inform pedestrian and bicycle crash risk
Identify Risk
Factors
• Traffic and geometric characteristics
present at fatal and severe-injury
crash sites
Select and
Prioritize
Locations
• Segments exhibiting
one or more risk
factors
Develop
Systemic
Safety Projects
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• Apply countermeasures
to address risk factors at
specific locations
Data-Informed Safety Management Plan Example
Bend, OR
• Goal: Establish a safety
management program
– Understand crash
patterns
– Prioritize safety projects
– Improve collaboration
with other agencies
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Current
Limitations
Opportunities
Perceived
Safety
Objective
Safety
Reactive
Proactive
One-time
Repeatable
Individual
Efforts
Coordinated
Efforts
Data-Informed Safety Management Plan Example
Bend, OR
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Corridor Safety Analysis Example: SR 46
• Facility: 7.4 miles of two-lane rural highway in
Seminole County, Florida
• Goal: Evaluate crash history and identify
countermeasures to reduce crash frequency and
severity
– Identify project
cost-benefit ratios to justify
funding and objectively
prioritize projects
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Corridor Safety Study Example: SR 46
•
•
Corridor crash trends
– 30% rear-end
– 24% run-off-road
– 45% at night
Contributing Factors
– Careless Driving
– Failure to Yield ROW
– Speed
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Corridor Safety Study Example: SR 46
Location
SR 415 to Richmond Ave
SR 46 / Richmond Avenue
Richmond Ave to
Mullet Lake Park Road
SR 46 / Mullet Lake Park
Road
Mullet Lake Park Rd to
Avenue C
SR 46 / Avenue C
Avenue C to CR 426
SR 46 / CR 426
Total
Observed Annual
Number of Crashes
0.2
1.8
Predicted Number Expected Number
of Crashes per
of Crashes per
Year
Year
0.8
0.6
1.1
1.4
6.2
12.7
10.4
0.2
1.6
0.9
5.2
7.3
6.4
0.2
2.0
5.0
20.8
2.8
2.3
3.1
31.7
1.7
2.2
3.6
26.8
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Corridor Safety Study Example: SR 46
Location
·
Mullet Lake Park ·
Rd to Avenue C ·
·
SR 46 &
·
·
Avenue C
·
Avenue C
·
to CR 426
·
·
·
SR 46 &
·
CR 426
·
Project Countermeasures
Install centerline rumble strips
Install shoulder rumble strips
Install intersection warning signage
Pave gravel approach at Torren Pt
Install intersection warning signage
Provide a N/WB left-turn lane on SR 46 at Woodbridge
Install centerline rumble strips
Install shoulder rumble strips
Install Intersection warning signage
Install retroreflective tape on signal Ahead sign pole
Install street name plaque at Signal Ahead sign
Relocate stop bars to improve sight distance for RTOR
Upgrade intersection signage, internally illuminated signs
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No-Build
Project Construction
Crash
CMF
Cost
Costs
Build
Crash
Costs
74%
$87,000
$8,813,000 $6,518,000 $
72%
$1,000
$2,377,000 $1,711,000
74%
$22,000
$2,842,000 $2,102,000
77%
$9,000
$2,993,000 $2,305,000
Corridor Safety Study Example: SR 46
• Tier I Projects
• Low-cost rumble strips, signs
• Tier II Projects
• Moderate-cost shoulder widening, turn lanes, intersection
lighting, etc.
• Tier III Projects
• High-cost passing lane, access management
Project Tier
I
Total
Project Cost
Project Cost Project Benefit
Thru 2020
Thru 2020
Average
B/C Ratio
$472,000
$258,000
$7,495,000
29.1
II
$1,164,000
$636,000
$1,452,000
2.3
III
$2,870,000
$1,570,000
$1,769,000
1.1
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What’s Next?
• 2nd Edition Production through NCHRP 17-73
– Incorporates Freeway and Ramp Prediction Models
(Available now)
– Additional Models (e.g., arterials with six or more lanes and
one-way arterial streets)
– Increased statistical rigor
– Exclude Part D CMFs
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Questions?
• Brian Ray
– [email protected]
– 503-228-5230
• Casey Bergh
– [email protected]
– 541-312-8300
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