HSM Practioner's Guide for Two-Lane Rural Highways Workshop HSM Practitioner’s Guider for Two-Lane Rural Highways Workshop HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Exercise II – US 52 from Sageville to Holy Cross – Prediction of Safety Performance for Curves and Comparison to Substantive Safety Performance - Session #5 Session #5 – Exercise II – US 52 in Iowa (west of DuBuque and the Mississippi River) – Prediction of Safety Peformance for curves and Comparison to Substantive Safety Performance Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

Exercise II – US 52 from Sageville to Holy Cross HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Outcomes: Identify Curve Crashes Predict crash frequency for base conditions using SPF Base Model Apply CMFs for existing conditions to predict the safety performance of Curves Compare predicted safety performance of Curves to actual safety performance Learning Objectives for Session #5 – Exercise II – Prediction of safety performance for horizontal curves Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 1996 - 2000 Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

HSM Practioner's Guide for Two-Lane Rural Highways Workshop Exercise II – US 52 from Sageville to Holy Cross HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Geometric Information: Length: 13.0 miles ADT: 2,500 Lane Width: 11 feet Shoulders: Paved 0 feet Gravel 4 feet Hazard Rating: 5 Driveways: 91 (none on curves) Total Length of Curves = 4,826 ft or 0.914 mi US 52 Geometric Plan information Traffic Volume (AADT): 2,500 vehicles per day Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Exercise II – US 52 from Sageville to Holy Cross Geometric Information: Curves - no spirals Curve # Delta Radius Length S.V. fo e 1 104 deg 670.15 ft 1,225.5 ft 0.01 2- “A” 104 deg 33’ 836.6 ft 1162 ft 0.00 3- “B” 63 deg 56’ 477.5 ft 532.8 ft 4- “C” 67 deg 04’ 558.9 ft 5- “D” 42 deg 15’ 352 ft 6- “E” 62 deg 58’ 524.8 ft 0.02 7- “F” 28 deg 10’ 955 ft 469.4 ft US 52 Geometric Plan information Total Curve Lengths = 4,826 feet = 0.914 mi Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

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 Crashes by location Session 2 – Exercise I

Exercise II – US 52 from Sageville to Holy Cross HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Exercise II – US 52 from Sageville to Holy Cross From the US 52 corridor crash information, perform the following: (a) Identify Curve Crashes and (b) Determine Predicted Crash Frequency for base conditions for the 7 Horizontal Curves (crashes/year) Compute CMF3r and CMF4r for the 7 horizontal curves on US 52. Apply appropriate CMFs to determine the Predicted Crash Frequency for existing conditions for the curved sections (crashes/year) Compare the Actual Crash History (Substantive Performance) to the Predicted Crash Frequency (crashes/yr) Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

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 1 (a): Identify Crashes on Curves Session 2 – Exercise I

Exercise II – US 52 from Sageville to Holy Cross HSM Practioner's Guide for Two-Lane Rural Highways Workshop Exercise II – US 52 from Sageville to Holy Cross August 2010 1 (b). Compute the Predicted Crashes on Horizontal Curves for base conditions: For the 7 Horizontal Curves: Nspf-rs curves1-7 = (ADT) (Lcurve)(365)(10-6)e-0.312 = (2,500)(Lcurve x)(365)(10-6)e-0.312 Using the SPF Base Model calculate the predicted curve crashes for base conditions for each of the 7 curve lengths. Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Exercise II – US 52 Curves Nspf-rs = (AADTn) (L) (365) (10-6) e-0.3.12 1.(b): Curve Information: No Spirals Curve Radius (ft) Lc (ft) Lc (mi) Spiral (S) S.V. Nspf-rs 1 670 1,226 0.232 0.01 0.155 2- “A” 837 1,162 0.220 0.00 0.147 3- “B” 478 533 0.101 0.067 4- “C” 559 0.106 0.071 5- “D” 352 0.045 6- “E” 525 0.099 0.02 0.066 7- “F” 955 469 0.089 0.059 US 52 Geometric Plan information Table of geometric data (radius, lengths, presence of spirals, superelevation variance) and resulting calculation for Predicted Crash Frequency for Base Conditions (Nspf-rs). Total: 0.914 mi Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

Exercise II – US 52 from Sageville to Holy Cross HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Use Worksheet Exercise II Compute CMF3r and CMF4r for the 7 horizontal curves on US 52. Apply appropriate CMFs to determine the Predicted Crash Frequency for existing conditions for the curved sections (crashes/year) a. Apply appropriate CMFs to the 7 Horizontal Curves (Use values for CMF1r CMF2r & CMF10r from Exercise I): Determine/calculate the appropriate CMFs for existing geometric conditions for the seven horizontal curves. Assume roadway geometric conditions are the same as the tangent segments for Lane Width, Shoulder Width & Type, and Roadside Hazard Rating/Roadside Design. CMF1r for Lane width CMF2r for Shoulder width and type CMF 3r for Horizontal Curves CMF 4r for Superelevation Variance CMF10r for Roadside Hazard Rating (Roadside Design) Npredicted-rs curves = Nspf-rs curves (CMF1r x CMF2r x CMF3r x CMF4r x CMF10r) Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 Exercise II – US 52 Curves Nspf-rs = (AADTn) (L) (365) (10-6) e-0.3.12 Eqs: 10-14, 15, & 16 US 52 Geometric Plan information Table of geometric data (radius, lengths, presence of spirals, superelevation variance) and resulting calculation for Predicted Crash Frequency for Base Conditions (Nspf-rs). Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

Exercise II – US 52 from Sageville to Holy Cross HSM Practioner's Guide for Two-Lane Rural Highways Workshop August 2010 4. Compare the Actual Crash Frequency per year to the Predicted Crash Frequency for the curves Actual Curve crashes = 39 / 5 years = _____ crashes per year Npredicted-rs curves = _____ crashes per year Comparing the predicted value (1.3 crashes per year) to the actual safety performance of the curves (7.8 crashes per year). The fact that actual crashes are 6 times greater then predicted implies that safety countermeasures are needed to reduce the potential of curve related crashes. Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

Exercise II – US 52 from Sageville to Holy Cross HSM Practioner's Guide for Two-Lane Rural Highways Workshop Exercise II – US 52 from Sageville to Holy Cross August 2010 Outcomes: Identified Curve Crashes Predicted crash frequency for base conditions using SPF Base Model Applied CMFs for existing conditions to predict the safety performance of Curves Compared predicted safety performance of Curves to actual safety performance Learning Objectives for Session #5 – Exercise II – Prediction of safety performance for horizontal curves Session 5 – Predicting Highway Safety for Curves for 2-Lane Rural Highway Segments

Questions and Discussion: HSM Practitioner's Guide for Two-Lane Rural Highways August 2010 Exercise I: US 52 from Sageville to Holy Cross Questions and Discussion: