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(civl261)[2009](s)quiz6b~PPSpider^_10069.pdf
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CIVL 261 C Traffic and Transportation Engineering
Tutorial Quiz 6B March 25, 2009
Name : Student ID :
Geometric Design of Highways C Crest Vertical Curve
For a design speed of 60 mph, f = 0.29, calculate the minimum length of a crest vertical curve with G1=+3 % and G2= -1 % that meets the 1984 AASHTO criteria for minimum SSD and desirable SSD.

Solution:
Design speed = 60 mph. From Table 3.1, the speed condition is distributed between 52 mph and 60 mph.

Minimum SSD
For minimum SSD, we use average running speed at 52 mph.
So


Assuming SSD > L, then


Assuming SSD < L, then


So, the minimum length of the crest curve is 878ft.

Desirable SSD
For desirable SSD, we use design speed at 60 mph.
So


Assuming SSD > L, then


Assuming SSD < L, then


So, the minimum length of the crest curve is 1412ft.