Level of Service

[mustangcobra93]

I was working some level of service problems for mutilane highways and two lane highways last night and had a couple questions. In one example the truck percentage was 8%, bus percentage 2% and RV percentage was 2%. I thought that when the percentage of trucks and buses were greater than or equal to 5 times the percentage of RV's the RV's part of the equation for the heavy vehicle factor could be left off. However, in the solutions the entire equation was used. What is the correct way?

Also, in each example a directional distribution was given, but in the solution it was not used except in the two lane highway case in order to get a value from a table in the HCM. I thought if the distribution was given the larger number would be multiplied by the given V. Is this not true?

 

[maximus808]

According to the HCM, the 5 times RV to omit rule is applicable only to Basic Freeway Segments, not two lane or multilane highways. Also, typically I believe directional distribution applies to two lane highways only as the opposing direction of traffic has an impact on the lane group being analyzed. This info is from the HCM as well.

 

[mustangcobra93]

Thatnks for the info. I reread the HCM last night and realized I had made the mistake of taking the five times rule out of context when it should only have been used for freeway segments.

 

[maximus808]

Honestly I find the layout of the HCM sample problems to be so much more organized and easier to follow than the CERM or PPI's study material. But in any case, just knowing the different sections of the HCM and where to look for certain factors/equations are essential. Keep those questions coming

 

[NEED2009]

Do the problems provided by HCM will give you a good understanding of the process for these type of questions on the exam.