Texas-wide GIS-based Crash Risk Assessment · Texas-wide GIS-based Crash Risk Assessment By Michael...
Transcript of Texas-wide GIS-based Crash Risk Assessment · Texas-wide GIS-based Crash Risk Assessment By Michael...
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Texas-wide GIS-based Crash Risk Assessment
By Michael Martin
2015 Traffic Safety Conference Corpus Christi, Texas
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Overview
The Concept
The Process – Road Segments Defined – Crashes Assigned to Road Segments – Crash Rates Calculated per Road Segment – Traffic Volume Ranges Defined – Crash Risk Categories Assigned
Statewide Crash Risk Map
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The Concept
• TTI report PRC 14-27-F Safety section
• To compare crash risks for like road segments with similar:
– Functional class
– Area type
– Traffic volume
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Road Segments Defined
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Crashes Assigned
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Crash Rates Calculated Per Road Segment
# 𝑜𝑜 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐿𝐶𝐿𝐿𝐿𝐶 ∗ 𝐴𝐴𝐴
The probability of being involved in a crash per instance of the exposure measure (length and traffic volume combined).
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Traffic Volume Ranges Defined
Area Type Functional Class
Volume Ranges (ADT)
Low Medium High
Urban
Freeways <75,000 75,000 – 150,000 >150,000
Arterials <25,000 25,000 – 50,000 >50,000
Collectors <5,000 5,000 – 10,000 >10,000
Local* 0 – 20,000
Rural
Freeways <30,000 30,000 – 60,000 >60,000
Arterials <15,000 15,000 – 30,000 >30,000
Collectors <5,000 5,000 – 10,000 >10,000
Local* 0 – 15,000
*- Only one volume group.
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Traffic Volume Ranges Defined Crashes per Mile vs. Traffic Volume (ADT) for
Rural Freeways
Low High Medium
0
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0 20000 40000 60000 80000 100000 120000 140000 160000
Cras
hes p
er M
ile
Traffic Volume (ADT)
Inflection points where the relationship between crash rate per mile and volume change.
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Crash Risk Categories Assigned
Area Type Functional Class
Volume Ranges (ADT)
Low Medium High
Urban
Freeways <75,000 75,000 – 150,000 >150,000
Arterials <25,000 25,000 – 50,000 >50,000
Collectors <5,000 5,000 – 10,000 >10,000
Local* 0 – 20,000
Rural
Freeways <30,000 30,000 – 60,000 >60,000
Arterials <15,000 15,000 – 30,000 >30,000
Collectors <5,000 5,000 – 10,000 >10,000
Local* 0 – 15,000
*- Only one volume group.
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Crash Risk Categories Assigned
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
0 1 2 3 4 5 6 7 8 9 10
Perc
ent o
f Seg
men
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Crash Rate (Crashes per Million Vehicle-Miles)
Inflection points where the relationship between cumulative percentages and crash rates change.
Low
Moderate
High Very High
Cumulative Percentage vs. Crash Rate for Medium Traffic Volume Rural Freeways
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All 20 Groupings
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All 20 Groupings with High & Very High Risk