Transcript No Slide Title

Rural Intersection
Decision Support
Crash Analysis
Presented at
Pooled Fund Meeting
April 19, 2004
Page 2
Overview
•
•
•
•
The Goals
Process for Individual States
Crash Analysis
What We Need
The Goals
• Statewide Review of Rural Thru-STOP
Intersections to Identify Patterns.
– Two-Lane
– Expressway
– Other?
• Identify Candidate Intersections for Field
Deployment.
– Focus on locations with a documented safety deficiency
and crashes susceptible to correction by installation of the
Driver Infrastructure Interface (DII).
– Detailed review of up to 5 intersections.
Process for Individual States
• Visit State DOT
– Collect available crash information.
– Learn about the crash record system’s characteristics.
– Discuss where analysis should be focused (i.e., two-lane
or expressway or both).
• Crash Analysis
– Identify pool of potential candidate intersections.
– Screen/prioritize candidate intersections using Critical
Crash Rate, crash severity and frequency of crashes
susceptible to correction (i.e., straight crossing path).
– Identify Top 5 Intersections for field deployment.
Process for Individual States
• State Review
– Review, adjust, and/or approve Top 5 candidate
intersections.
• More Crash Analysis
– Detailed review of final Top 5 candidates.
• Visit State DOT
– Present findings from the Statewide review and for the
Top 5 candidate intersections.
– State selects intersection for field deployment.
Crash Analysis The Minnesota Process
All Rural Thru-STOP
Intersections
Separate
by facility
type.
4-Legged;
Two-Lane
Roadways
Candidate
Intersections,
Two-Lane
Advantages of the MN Process:
- Research team familiar with this process,
- Provides for statistical reliability, and
- Identified MN intersection which
agencies agreed upon.
State DOT
Selection of
Test Intersection
4-Legged;
Expressways
Identify
intersections
over the
critical crash
rate.
Candidate
Intersections,
Expressways
Detailed
review
of crash
conditions.
Identify intersections
with high crash frequency,
severity, and number of
crossing path crashes.
Top 5
Candidates
Crash Analysis Statewide Review
All Rural Thru-STOP
Intersections
Separate
by facility
type.
1,174 Intersections
Crash Rate = 0.5
Severity Rate = 0.9
3,784 Intersections
Crash Rate = 0.4
Severity Rate = 0.6
198 Intersections
Crash Rate = 0.4
Severity Rate = 0.7
4-Legged;
Two-Lane
Roadways
4-Legged;
Expressways
State DOT
Selection of
Test Intersection
Candidate
Intersections,
Two-Lane
Candidate
Intersections,
Expressways
Top 5
Candidates
Crash Analysis Statewide Review
• Begin with all rural thru-STOP intersections.
– Need to be able to identify intersection by:
• Location - Rural vs. Urban
• Intersection Control - Thru-STOP
• Facility Type through roadway - Two-Lane vs. Expressway
– Intersections with 4 approaches are preferred.
• For each group of intersections, determine the
“expected”
– Crash rate,
– Severity rate, and
– Crash type distribution.
Crash Severity Factors:
Fatal = ?
“A” Inj. = ?
“B” Inj. = ?
“C” Inj. = ?
PDO = ?
(MN = 5)
(MN = 4)
(MN = 3)
(MN = 2)
(MN = 1)
Crash Analysis Identify Candidate Intersections
All Rural Thru-STOP
Intersections
104 Intersections
Crash Rate = 1.6
Severity Rate = 2.9
4-Legged;
Two-Lane
Roadways
Candidate
Intersections,
Two-Lane
State DOT
Selection of
Test Intersection
4-Legged;
Expressways
Identify
intersections
over the
critical crash
rate.
Candidate
Intersections,
Expressways
23 Intersections
Crash Rate = 0.9
Severity Rate = 1.8
Top 5
Candidates
Crash Analysis Identify Candidate Intersections
• Use Critical Crash
Rate to Identify
Candidate
Intersections
– Statistically accounts for
random nature of
crashes.
+
Crash Analysis Identify Top 5 Candidates
All Rural Thru-STOP
Intersections
4-Legged;
Two-Lane
Roadways
4-Legged;
Expressways
Candidate
Intersections,
Two-Lane
Candidate
Intersections,
Expressways
State DOT
Selection of
Test Intersection
Identify intersections
with high crash frequency,
severity, and number of
crossing path crashes.
Top 5
Candidates
Crash Analysis Identify Top 5 Candidates
• Screen Candidate Intersections for Top 5
Candidates Based on:
– High crash frequency,
– High crash severity,
• Fatal and Serious Injury crashes
– High number of crashes susceptible to
correction by installation of the DII.
• Right angle…see following slide
Correctable Crash Types
GES Crossing
Path Crash
Designations
Example Crash Type Reporting Differences
Mn/DOT Crash Type
Right Angle
Left Turn into Oncoming Traffic
Right Turn into Cross-Street,
Traffic from Left
GES Crash Type
Left Turn Across Path – Lateral Direction (LTAP/LD)
Left Turn Into Path – Merge (LTIP)
Straight Crossing Path (SCP)
Left Turn Across Path – Opposite Direction (LTAP/OD)
Right Turn Into Path – Merge (RTIP)
Crash Analysis - State DOT
Selection of Test Intersection
All Rural Thru-STOP
Intersections
4-Legged;
Two-Lane
Roadways
4-Legged;
Expressways
State DOT
Selection of
Test Intersection
Detailed
review
of crash
conditions.
Candidate
Intersections,
Two-Lane
Candidate
Intersections,
Expressways
Top 5
Candidates
Crash Analysis - State DOT
Selection of Test Intersection
• Review crash records for factors that
may identify best candidate.
–
–
–
–
–
At-Fault driver’s age
Severity of correctable crashes
Crash type distribution
Weather and visibility conditions
Contributing factors
NOTE:
May need access to Police
Officer reports to determine
the at-fault driver and identify
the contributing factors.
• Ran-the-STOP
• Stopped, Pulled Out
– Crash location for divided roadways
• Farside
• Nearside
What We Need...
• For the Statewide Crash Analysis
– Expected crash rate and severity rate for “similar”
intersections OR crash summary for all rural thru-STOP
intersections (see next slide).
– Intersection approach volumes.
– Crash records for rural thru-STOP intersections from the
past 3 years.
– Crash record information should include at least the
• Crash Type/Diagram and
• Crash Severity.
Example Mn/DOT Crash File
Statewide Intersection Summary
Information can be used to determine expected
rates for a group of intersections and if individual
intersections are above the critical crash rate
(i.e., candidate intersections).
Intersection Attributes:
- Rural vs. Urban
- Traffic Control Device
- Roadway type
Example Mn/DOT Crash File
Intersection Crash Report
Information can be used to
identify Top 5 Candidates.
Imported into Excel
What We Need...
• For the Analysis of Top 5 Candidates
– Crash record information also needs to include
• At-Fault driver’s information,
•
•
•
•
Roadway surface conditions,
Weather and visibility conditions,
Contributing factors, and
Crash location.
– May need police officer reports from the past 3 years.
Example Mn/DOT Crash File
Intersection Crash Report
Light - 1 = Daylight
2 = Sunrise
Etc.
Weather - 1 = Clear
2 = Cloudy
3 = Rain
Etc.
Information can be used to
screen the Top 5 Candidates.
Action - 1 = Straight
6 = Left Turn
Etc.
Factor - 2 = Failure to Yield
3 = Speed
15 =Inattention
Etc.
In Conclusion
• Following this process in Minnesota resulted in
the identification of a large pool of candidate
intersections.
• The prioritization process screened the
intersections down to a Top 3 short list.
• The supplemental analysis provided the
information that supported Mn/DOT’s selection
of an intersection for the Field Operations Test.
– US 52 and Goodhue County 9.
• Next Steps
– Meetings with Individual State DOT Technical Liaisons.
– Obtaining individual State’s crash records.
– Analysis of the data.
Questions