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Does 24+0=22+2? An Intro to HSM Methods. Jason J. Siwula, PE – Safety Engineer. Does 24+0=22+2?. On the surface it appears that 24=24 Sometimes items are not as simple as they seem…. 24 = 24. I see you x!. Placement makes a world of difference!.
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Does 24+0=22+2?An Intro to HSM Methods Jason J. Siwula, PE – Safety Engineer
Does 24+0=22+2? • On the surface it appears that 24=24 • Sometimes items are not as simple as they seem… 24 = 24
Placement makes a world of difference! Edgeline on edge of pavement with no room for shoulder Edgeline placed with room for shoulder
Example Case Study Source: Hillary Isebrands (FHWA Office of Safety)
Example Case Study (continued) • Q: When resurfaced, can we influence safety on this roadway without utilizing any additional funds to do so? • A: Yes, with the HSM we can examine different lane/shoulder combinations to determine the best layout of the markings for safety performance.
Example Case Study continued Existing Conditions 11 ft. lanes, 1 ft. shoulders
What does that mean? Using the SPF for 2 lane rural highways for a 10 miles segment with 10,000 vpd we would estimate a base number of crashes to be 26.72 crashes per year. Existing Conditions 11 ft. lanes, 1 ft. shoulders 26.72*1.29=34.47 crashes per year (344.7 crashes in 10 years) 26.72*1.26=33.66crashes per year (336.6 crashes in 10 years) That’s a predicted savings of 8.1 crashes over 10 years!
What is the HSM? • The Highway Safety Manual (HSM) introduces a science-based technical approach that takes the guesswork out of safety analysis • Provides tools to conduct quantitative safety analyses, allowing for safety to be evaluated alongside other transportation performance measures Source: http://www.highwaysafetymanual.org/Documents/HSMP-1.pdf
HSM Part C – Predictive Method • Introduces Safety Performance Functions (SPFs) • Predictive method for estimating expected average crash frequency of a: • Network • Facility • Individual Site
HSM in Kentucky? • Utilize HSIP funds to purchase HSMs for each District as well as the Central Office • Utilize HSM predictive methods in project evaluation and prioritization for new projects • KYTC Safety Engineers are evaluating the accompanying software package SafetyAnalyst for possible future implementation
Interested in the HSM? • http://www.highwaysafetymanual.org • http://safety.fhwa.dot.gov/hsm/ • http://www.cmfclearinghouse.org