Jason J. Siwula, PE – Safety Engineer

DOES 24+0=22+2?AN INTRO TO HSM METHODS

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!

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?

26.72*1.29=34.47 crashes per year

(344.7 crashes in 10 years)

26.72*1.26=33.66 crashes per year

(336.6 crashes in 10 years)

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.

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

Questions?