1. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
HW 7: US 52 from Sageville to Holy Cross – Prediction of Safety Performance and Comparison
to Actual Safety
Performance
Session #3 – Exercise I – US 52 in Iowa (west of DuBuque and the Mississippi River) – Prediction of Safety Peformance and Comparison to Substantive Safety Performance
Session 2 – Exercise I

2. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Learning Outcomes:
Identify Crashes by type
Apply models for safety performance to Level and On-Grade Tangent Segments
Compare predicted crash frequency performance to actual safety performance
Identify crash patterns that are over-represented
Learning Objectives for Session #1 Introduction and Background for Intersection Safety
Session 2 – Exercise I

3. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Session 2 – Exercise I

4. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Session 2 – Exercise I

5. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Crashes by severity
Fatalities
Injuries – Major
Injuries – Minor 29
Injuries – Possible Injury 22
PDO
Total 122
Session 2 – Exercise I

6. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
Collision Types
HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Total: 122
Session 2 – Exercise I

7. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
Segments/Grade/Curves
August 2010
LOCATION
NUMBER
On Roadway Segments 63
Within Intersection 16
Intersection Related 1
On-Grades 3
On Curves 39
Total
122
Crashes by location
Session 2 – Exercise I

8. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
US 52 Geometric Plan information
Session 2 – Exercise I

9. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Geometric Information:
Length: miles
AADT: 2,500
Lane Width: 11 feet
Shoulders: Paved 0 feet
Gravel 4 feet
Hazard Rating: 5
Driveways: (on level tangent sections)
Total Length of Curves = 4,826 ft or mi
Total Length of Grades = 13,400 ft or 2.54 mi
US 52 Geometric Plan information
Session 2 – Exercise I

10. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Grade Section #
% Grade
Length in ft 1
5.6%
200 2
3.95
450 3
3.875
300 4 6
3200 5
5.2 7
700 8
5.4
350 9
3.05
400 10
900 11
5.9
1950 12
1700 13
1050 14
3.9
1150 15
4.8
150
Geometric Information: Grades:
Total Length = 13,400 feet or 2.54 miles
US 52 Geometric Plan information
3%< All Grades <6%
Session 2 – Exercise I

11. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
From the US 52 corridor crash information, perform the following:
1a: Identify crashes by type (Segment, Intersection, Curves)
1b: Compute the Severity Index (SI) for the 13 miles of US 52?
SI = Fatal + Injury Crashes
Total Crashes
1c: Is the Severity Index higher or lower than normal?
Session 2 – Exercise I

12. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Predict the Crash Performance for the following:
SPF Base Model for US 52 Segment (level alignment), excludes grades and curves)
SPF Base Model for US 52 Segment (on-grade segments only)
Determine CMFs for Level Tangent and On-Grade Tangent Segments and apply the CMFs to the SPF Base Model Lane Width, Shoulders, Driveway Density, and Roadside Design
Determine the Total Predicted Crashes for Level and On-Grade Segments
Session 2 – Exercise I

13. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Compare the predicted number of crashes per year for Level and On-Grade Tangent Segments with the Actual Safety Record and answer the following Question:
“Is the actual crash frequency performance for the geometrics for US 52 for existing conditions less than the Predicted Crash Frequency?”
Session 2 – Exercise I

14. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
August 2010
Identify crashes by type & Compute S.I.
Compute Predicted Crashes for:
Discussion
SPF Base Model (Level Tangent Segments)
SPF Base Model for On-Grade Tangent Segments
SPF Base Model x CMF’s for both Segment above
Total Predicted Crashes for both segments above
Pause at this slide; continue on when participants have worked on the exercise.
Is actual Safety performance better than predicted?
Use Worksheet Exercise I
Session 2 – Exercise I