1. HSM Practitioner’s Guider for Two-Lane Rural Highways Workshop
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross – Prediction of Safety Performance for Intersections
Session #7 – Exercise III – US 52 in Iowa (west of DuBuque and the Mississippi River) – Prediction of Safety Peformance for Intersections and Comparison to Substantive Safety Performance
- Session #7
Session 7 – Exercise III - Intersections

2. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Learning Outcomes:
Select Intersection Crashes out of Total Crashes
Apply SPF Base Model equations for prediction of crash frequency performance
Compare predicted crash frequency to Substantive Safety performance
Learning Objectives for Session #9 – Exercise III – Prediction of safety performance for Intersections on US 52
Session 7 – Exercise III - Intersections

3. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Session 7 – Exercise III - Intersections

4. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Session 7 – Exercise III - Intersections

5. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
Exercise III: US 52 from Sageville to Holy Cross – 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

6. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Stop-Controlled Intersections on US 52: (AADTmaj = 2,500)
Station
Location
Type
Side Road ADT
Predicted Crashes
Skew
Crashes x CMF
107
East of D
3-leg
450
15 deg
126
West of D
250
5 deg
262
East of F
70 deg
559 F
4-leg
300
0 deg
TOTAL ?
Complete the table: Predicted crashes of the four stop-controlled intersections and their AMF for skew. Sum the results to obtain the total number of predicted crashes for the four intersections.
Session 7 – Exercise III - Intersections

7. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Compute the predicted crashes for the four (4) intersections on US 52
Compare the Actual Crash Frequency to the Predicted Crash Frequency per year for the Intersections
Discussion
Pause at this slide; continue on when participants have worked on the exercise.
Use Worksheet Exercise III
Session 7 – Exercise III - Intersections

8. HSM Practicitioner's Guide for Two-Lane Rural Highways Workshop
Exercise II: US 52 from Sageville to Holy Cross – 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
Identify IntersectionCrashes
= 17
Session 2 – Exercise I

9. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
“T” Intersection East of F:
A “T” Intersection in eastern Iowa on US 52
ADT on US 52 is 2,500
ADT on side road is 450
US 52 in Iowa – “T” Intersection (looking at one intersection)
Actual crashes were 4 in 5 years or 0.8 per year at the “T” Intersection.
3 crashes involve a left turning vehicle from US 52 and one is an angle crash for a vehicle pulling out from the stem of the “T”
Of the 4 crashes in 5 years, 3 were at night.
Session 7 – Exercise III - Intersections

10. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Calculation: “T” Intersection East of F:
3-legged intersection, Major Road AADT = 2,500 vpd, Minor Road AADT = 450 vpd, Calculate predicted crashes for the intersection:
Nspf-3ST = exp[ ln(AADTmaj) ln(AADTmin)]
= exp[ ln(2,500) ln(450)]
Demonstrated calculation for the 3-leg (T) intersection East of F. Crash history shows 4 crashes in 5 years which equates to 0.8 crashes per year which is 60% greater then our predicted value of 0.5 crashes per year.
= exp[ ]
= exp[-0.685]
= crashes per year
Session 7 – Exercise III - Intersections

11. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
“T” Intersection East of F:
3-legged intersection, Skew = 70 degrees. Calculate AMF for SKEW:
CMFskew , East of F = e(0.0040(Skew)
= e(0.0040(70)
Demonstrated calculation for AMF for Skew (i.e, AMF1i) for the Intersection East of F.
= e(0.280)
= 1.323
Session 7 – Exercise III - Intersections

12. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
“T” Intersection East of F:
3-legged intersection, Major Road AADT = 2,500 vpd, Minor Road AADT = 450 vpd, Skew = 70 degrees Calculate total predicted crashes for the intersection:
Nintersection = NEast of F x CMFskew
= x 1.323
Demonstrated calculation applying AMF for Skew to the SPF Base Model for the Intersection East of F results: Npredicted = crashes per year.
= crashes per year
Session 7 – Exercise III - Intersections

13. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Intersections on US 52 (AADT = 2500):
Station
Location
Type
Side Road AADT
Predicted Crashes/ year
Skew CMF
Crashes x CMF
107
East of D
3-leg
450
0.504
1.062
0.535
126
West of D
250
0.378
1.020
0.385
262
East of F
1.323
0.667
559 F
4-leg
300
0.680
1.000
TOTAL
2.27
Table of completed calculations using the SPF Base Model and AMF’s for Skew. For the four intersections: Total Npredicted = crashes per year.
Session 7 – Exercise III - Intersections

14. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
From the US 52 corridor crash information, perform the following:
Compare the actual crash frequency per year with the Predicted Crash Frequency performance for the Intersections
Actual Crash Frequency = 17 crashes / 5 years
= 3.4 crashes / year
Predicted Intersection
Crash Freuency = 2.3 crashes/year
Actual = 50% > predicted crashes
Session 7 – Exercise III - Intersections

15. Exercise III – US 52 from Sageville to Holy Cross
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Exercise III – US 52 from Sageville to Holy Cross
Learning Outcomes:
Selected Intersection Crashes out of Total Crashes
Applied SPF Base Model equations for prediction of crash frequency performance
Compared predicted crash frequency to Substantive Safety performance
Learning Objectives for Session #9 – Exercise III – Prediction of safety performance for Intersections on US 52
Session 7 – Exercise III - Intersections

16. Questions and Discussion
HSM Applications to Two-Lane Rural Highways
Safety and Operational Effects of Geometric Design Features for Two-Lane Rural Highways Workshop
May 2009
Questions and Discussion
Session 7 – Exercise III - Intersections