Quiz #13

An intersection experiences 25 crashes per year. The installation of advanced warning beacons one half block before the intersection is expected to reduce the crash rate to 22 crashes per year, assuming the same ADT. What is the Crash Modification Factor (CMF) for the beacons?

A.) 0.12
B.) 0.88
C.) 1.13
D.) 3.00

B

CRF = (25-22)/25 = 0.12 = 12%

CMF = 1-(CRF/100) = 1-(12/100) = 0.88

I haven't even opened the HSM yet, but I'll go B .... it's gotta be A or B

B

I would take a guess for B) 0.88

:violin:

B it is.

I can't imagine the CMF problems on the new exam being any different than this.

Me too, the HSM is big. I haven't decided if I am gonna buy it or not.

I am not too familiar with the HSM either. I just basically randomly flipped to chapt three. I saw equation 3-5 on pg 3-19 and this example on page 3-20 which inspired me.

Crash Modification Factor Examples
Example 1
Using an SPF for rural two-lane roadway segments, the expected average crash frequency for existing conditions is
10 injury crashes/year (assume observed data is not available). The base condition is the absence of automated speed
enforcement. If automated speed enforcement were installed, the CMF for injury crashes is 0.83. Therefore, if there is
no change to the site conditions other than implementation of automated speed enforcement, the estimate of expected
average injury crash frequency is 0.83 × 10 = 8.3 crashes/year.

Yes, the book is large at 3 volumes and 17 chapters but, remember, the exam only tests on Vol 1, Chapts 1-9.

Awesome. I really did not see that it is only the first volume until you mentioned it. I have looked at the references list while ago. Thanks for pointing that out.

CMF is Volume 3 - Chapters 13-17 ???

I haven't even looked at this thing yet, and none of the review courses have touched this as well.

John Q said:

CMF is Volume 3 - Chapters 13-17 ???

I haven't even looked at this thing yet, and none of the review courses have touched this as well.

Click to expand...

Sorry JQ, what are you asking?

ptatohed said:

Yes, the book is large at 3 volumes and 17 chapters but, remember, the exam only tests on Vol 1, Chapts 1-9.

Click to expand...

This .... you pulled this from Volume 1?

Volume 3 is called CMF ????

John Q said:

ptatohed said:

Yes, the book is large at 3 volumes and 17 chapters but, remember, the exam only tests on Vol 1, Chapts 1-9.

Click to expand...

This .... you pulled this from Volume 1?

Volume 3 is called CMF ????

Click to expand...

As mentioned in my post #9, I got this from Chapt 3.

Chapt 3 is in Vol 1.

So I looked at this a little this morning .... It looks like Chapter 3 (V1) is really an introduction to CMFs and a lot of the basic math and theory.

Vol 3 - Crash Modification Factors, really gets down into the weeds with applying these to different road segments, geometrics, etc.

Seeing that there just aren't many people familiar with this document, and it is a new addition, I think Chapter 3 may be the only one I look at.

psucivil23 said:

B

CRF = (25-22)/25 = 0.12 = 12%

CMF = 1-(CRF/100) = 1-(12/100) = 0.88

Click to expand...

This is correct but you don't need two steps. CMF = (Crash Frequency of Modified Site b) / (Crash Frequency of Base Site a) = 22 / 25 = 0.88