Possible Part B Ch. 4 Error - Calculating LOSS

Errata, HSM knowledge gaps/research needs and potential errors and omissions

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Possible Part B Ch. 4 Error - Calculating LOSS

Postby benpdx » Tue Aug 05, 2014 12:53 pm


I've been using Level of Service of Safety (LOSS) for a network screening project and I think I've found a typo. It's on page 4-47 in Table 4-11, where the conditions for each LOSS category are listed.

Table 4-11: LOSS Categories
Screenshot_080514_114534_AM.jpg (75.4 KiB) Viewed 1592 times

Based on my understanding of the LOSS metric, there seem to be errors in the condition section of LOSS I and LOSS III.

LOSS I seems like it should not include the "sigma less than" part. The category seems like it should start at zero observed crashes, not at the standard deviation. If it did start there, there would be no applicable category for locations with zero crashes.

LOSS III seems to be missing the "less than" character between N observed and (N+1.5*sigma). This is necessary for it to be a valid range.

I hope this information is helpful to others. I would like to know if I am correct in my suspicions, and if this is an officially acknowledged errata yet - or if I'd have to wait for Errata #3 to be published to know that for sure. It'd be great to be able to cite something or someone in my report documenting this correction.

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