I'm taking the Civil: Transportation Depth Exam in less than two weeks and I'm stumped on one of the PPI: Exam Cafe AM Transpo questions. The solution said it was found in the Green Book but, I was only able to find the cross slope recommendation (1.5%-2%). I realize I can eliminate two using the cross slope and logically eliminate the gravel shoulders. But, is that what I'm suppose to do or is the ANSWER actually in the Green Book? Here is the question:
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.
Thank you!
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.
Thank you!