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

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

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

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 1996 - 2000 Session 7 – Exercise III - Intersections

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

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

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

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

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

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[-9.86 + 0.79 ln(AADTmaj) + 0.49 ln(AADTmin)] = exp[-9.86 + 0.79 ln(2,500) + 0.49 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[-9.86 + 6.18 + 2.99] = exp[-0.685] = 0.504 crashes per year Session 7 – Exercise III - Intersections

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

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 = 0.504 x 1.323 Demonstrated calculation applying AMF for Skew to the SPF Base Model for the Intersection East of F results: Npredicted = 0.667 crashes per year. = 0.667 crashes per year Session 7 – Exercise III - Intersections

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 = 2.267 crashes per year. Session 7 – Exercise III - Intersections

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

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

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