HSM Practitioners Guider for TwoLane Rural Highways Workshop

HSM Practitioner’s Guider for Two-Lane Rural Highways Workshop Exercise II – US 52 from Sageville to Holy Cross – Prediction of Safety Performance for Curves and Comparison to Substantive Safety Performance - Session #5 5 -1

Exercise II – US 52 from Sageville to Holy Cross Outcomes: è Identify Curve Crashes è Predict crash frequency for base conditions using SPF Base Model èApply CMFs for existing conditions to predict the safety performance of Curves èCompare predicted safety performance of Curves to actual safety performance 5 -2

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1996 - 2000 5 -4

Exercise II – US 52 from Sageville to Holy Cross Geometric Information: § Length: § ADT: § Lane Width: § Shoulders: 13. 0 miles 2, 500 11 feet 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 Traffic Volume (AADT): 2, 500 vehicles per day 5 -5

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 0. 00 4 - “C” 67 deg 04’ 477. 5 ft 558. 9 ft 0. 01 5 - “D” 42 deg 15’ 477. 5 ft 352 ft 0. 01 6 - “E” 62 deg 58’ 477. 5 ft 524. 8 ft 0. 02 7 - “F” 28 deg 10’ 955 ft 469. 4 ft 0. 01 Total Curve Lengths = 4, 826 feet = 0. 914 mi 5 -6

Exercise II: US 52 from Sageville to Holy Cross – Segments/Grade/Curves Crashes by location LOCATION On Roadway Segments NUMBER 63 Within Intersection 16 Intersection Related 1 On-Grades 3 On Curves 39 Total 122 5 -7

Exercise II – US 52 from Sageville to Holy Cross From the US 52 corridor crash information, perform the following: 1. (a) Identify Curve Crashes and (b) Determine Predicted Crash Frequency for base conditions for the 7 Horizontal Curves (crashes/year) 2. Compute CMF 3 r and CMF 4 r for the 7 horizontal curves on US 52. 3. Apply appropriate CMFs to determine the Predicted Crash Frequency for existing conditions for the curved sections (crashes/year) 4. Compare the Actual Crash History (Substantive Performance) to the Predicted Crash Frequency (crashes/yr) 5 -8

Exercise II: US 52 from Sageville to Holy Cross – Segments/Grade/Curves 1 (a): Identify Crashes on Curves LOCATION On Roadway Segments NUMBER 63 Within Intersection 16 Intersection Related 1 On-Grades 3 On Curves 39 Total 122 5 -9

Exercise II – US 52 from Sageville to Holy Cross 1 (b). Compute the Predicted Crashes on Horizontal Curves for base conditions: For the 7 Horizontal Curves: Nspf-rs curves 1 -7 = (ADT) (Lcurve)(365)(10 -6)e-0. 312 = (2, 500)(Lcurve x)(365)(10 -6)e-0. 312 5 -10

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 (mi) Spiral (S) S. V. Nspf-rs 1 670 1, 226 0. 232 0 0. 01 0. 155 2 - “A” 837 1, 162 0. 220 0 0. 00 0. 147 3 - “B” 478 533 0. 101 0 0. 067 4 - “C” 478 559 0. 106 0 0. 01 0. 071 5 - “D” 478 352 0. 067 0 0. 01 0. 045 6 - “E” 478 525 0. 099 0 0. 02 0. 066 7 - “F” 955 469 0. 089 0 0. 01 0. 059 Total: 0. 914 mi 5 -11

Exercise II – US 52 from Sageville to Holy Cross q. Use Worksheet Exercise II 2. Compute CMF 3 r and CMF 4 r for the 7 horizontal curves on US 52. 3. 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 CMF 1 r CMF 2 r & CMF 10 r from Exercise I): Npredicted-rs curves = Nspf-rs curves (CMF 1 r x CMF 2 r x CMF 3 r x CMF 4 r x CMF 10 r) 5 -12

Exercise II – US 52 Curves Nspf-rs = (AADTn) (L) (365) (10 -6) e-0. 3. 12 Eqs: 10 -14, 15, & 16 5 -13

Crash Modification Factor for Superelevation on Horizontal Curves CMF 4 r is based on “Superelevation variance” or SV ØFor SV less than 0. 01: CMF 4 r = 1. 00 ØFor 0. 01 < SV < 0. 02: CMF 4 r = 1. 00 + 6(SV-0. 01) ØFor SV > 0. 02: CMF 4 r = 1. 06 + 3(SV-0. 02) Example: Design e = 4%, Actual e = 2% SV = 0. 04 – 0. 02 = 0. 02 CMF 4 r = 1. 06 + 3(0. 02 -0. 02) = 1. 06 + 3(0. 0) = 1. 06 5 -14

Exercise II – US 52 Curves CMF 3 r = 1. 55 Lc + (80. 2/R) - 0. 012 S 1. 55 Lc 2 & 3: Curve Information: No Spirals Curve Nspf-rs LW CMF 1 r SW&T CMF 2 r Curve CMF 3 r S. V. CMF 4 r RD CMF 10 r 1 0. 155 1. 029 1. 093 1. 333 1. 000 1. 143 Np redicted Curves 0. 266 2 - “A” 0. 147 1. 029 1. 093 1. 281 1. 000 1. 143 0. 242 3 - “B” 0. 067 1. 029 1. 093 2. 072 1. 000 1. 143 0. 180 4 - “C” 0. 071 1. 029 1. 093 2. 022 1. 000 1. 143 0. 184 5 - “D” 0. 045 1. 029 1. 093 2. 624 1. 000 1. 143 0. 151 6 - “E” 0. 066 1. 029 1. 093 2. 089 1. 060 1. 143 0. 188 7 - “F” 0. 059 1. 029 1. 093 1. 610 1. 000 1. 143 0. 123 Total Predicted Curve Crashes Per Year = 1. 33 5 -15

Exercise II – US 52 from Sageville to Holy Cross 4. Compare the Actual Crash Frequency per year to the Predicted Crash Frequency for the curves Actual Curve crashes = 39 / 5 years = 7. 8 crashes per year Npredicted-rs curves = 1. 3 crashes per year 6 x’s > predicted value 5 -16

Exercise II – US 52 from Sageville to Holy Cross Outcomes: è Identified Curve Crashes è Predicted crash frequency for base conditions using SPF Base Model èApplied CMFs for existing conditions to predict the safety performance of Curves èCompared predicted safety performance of Curves to actual safety performance 5 -17

Exercise I: US 52 from Sageville to Holy Cross Questions and Discussion: 5 -18