Minimum Vertical Curve Length Requried for 15 mph road.

[tavo75]

Does someone know or point me in the right direction on what would be the minimum length needed for a vertical curve where i have an algebraic difference of 5.8%? The road has a 15mph limit for a residential area on a military base in Hawaii (Oahu). The road also T's into a road with a 25mph limit. The algegraic difference does not occur at the intersections but does occur about 30 from the intersection.

Thanks

 

[jeremyk55]

I wouldn't go any less than a K-value of 9. With a difference of 5.8%, it looks like you need a 55 to 60 foot curve. I would tie the curve to the cross slope of the other road.

 

[ACtrafficengr]

You left out a unit. 30 ft or 30 m?

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[Maury]

I checked the AASHTO publication "Geometric Design of Very Low-Volume Local Roads (ADT<400)".

For a 15 mph desighn speed, k=2.0

The length of the vertical curve would 35' for A=.058.

 

[jeremyk55]

Sorry, that K value was in feet. That came from the Indiana DOT Design Manual K value table for "comfort criteria" which is typically the lowest value they will allow without a design exception.

 

[ACtrafficengr]

Is it a sag or crest curve? If it is a crest, you'll need to make sure moving trucks won't get hung up. Especially since it is a military base, where people are constantly being reassigned, and moving in or out.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust