Posted 16 October 2011 - 09:16 PM
Problem 1: Transportation
A rural divided highway has an average daily traffic of 40,000 veh, with a design hour volume of 4,000 vehicles and a peak directional volume of 2500 vehicles. The commercial traffic is 5%. For a design speed of 70 mph, which of the following designs would be most appropriate?
a. four 12ft wide, paved lanes, with 8ft gravel shoulders and a cross slope of 1.5%
b. four 12ft wide, paved lanes, with 8ft paved shoulders and a cross slope of 4%
c. six 12ft wide, paved lanes, with 10ft paved shoulders and a cross slope of 2%
d. six 12ft wide, paved lanes, with 10ft gravel shoulders and a cross slope of 1%
SOLUTION: Using the AASHTO Green Book, for high traffic volumes, six lanes, and 10ft shoulders are desirable. The median should be at least 40 feet wide, and the cross slope of the pavement should be at least 1.5%. The answer is C.
Posted 17 October 2011 - 03:43 PM
You just need scroll this book very carefull. There are usulay enough questions from this book on the exam. You shoud be able to find your info quick.
Posted 17 October 2011 - 06:35 PM
And I agree w/the above poster -the answer is in the Green Book, typical cross sections.
Good luck with your studies!
Posted 17 October 2011 - 09:55 PM
Posted 18 October 2011 - 02:11 AM
Posted 19 October 2011 - 01:08 AM
Posted 19 October 2011 - 11:27 PM
As for the PPI problems, they are on the computer and NOT easy to print. Honestly, I'm not sure how much I'm going to use them besides emergency examples on the exam. They are pretty difficult, in my opinion, more difficult than the 6-minute solutions.
Starting to stress... so much left to practice, read, and tab! Good luck to all.
Posted 20 October 2011 - 04:52 PM
The lookup part is the number of lanes. HCM shows that for 70 mph with LOS = A (Assuming this is the design LOS. If provided, this would affect the number of lanes.), the flow rate is about 900 pc/h/ln. Using peak dir. volum of 2500, this mean you need 3 lanes to accommodate the peak flow in one direction. This narrows your answers to c and d.
The deduction part is about cross-slope, not the shoulder, because shoulder design for rural or urban environments isn't as crucial as cross-slope. The minimum cross-slope is mostly always 1.5%, thus eliminating answer "c", leaving us with "d".
This is a typical lookup/deduction question on the exam which tests a person's critical analysis skills rather than the rote manner of just looking up a table/graph or plugging and chugging an equation.
Posted 27 October 2011 - 02:59 AM
HCM (2000)Exhibit 21-2 "LOS Criteria for multilane highways" has max flow rates up to 60mi/h.
Edited by miloc, 27 October 2011 - 03:12 AM.
Posted 27 October 2011 - 12:42 PM
Free Flow Speed for rural area -70mph, for urban -75mph
good luck tomorrow
Also tagged with one or more of these keywords: transportation, exam cafe, AASHTO Green Book, breadth exam, PPI
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