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# Does 24+0=22+2? An Intro to HSM Methods - PowerPoint PPT Presentation

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

• On the surface it appears that 24=24

• Sometimes items are not as simple as they seem…

24 = 24

Edgeline on edge of pavement with no room for shoulder

Edgeline placed with room for shoulder

Source: Hillary Isebrands (FHWA Office of Safety)

• 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.

Existing Conditions

11 ft. lanes, 1 ft. shoulders

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!

• 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

• Introduces Safety Performance Functions (SPFs)

• Predictive method for estimating expected average crash frequency of a:

• Network

• Facility

• Individual Site

• 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

• http://www.highwaysafetymanual.org

• http://safety.fhwa.dot.gov/hsm/

• http://www.cmfclearinghouse.org