# NCEES Definition of 'Deflection Angle'



## ExhibitGuy (Apr 17, 2017)

Hi guys, I need your help:

I was working on problem #127 of the NCEES 2014 AM Civil Practice Exam, and the question gives the following:

*PI Station*: 12+40

*Degree of Curve*: 10°

*Deflection Angle*: 12°30'

*Find the station of the PT.*

The answer is 13+02.25. This seems like a pretty straightforward problem. However, I calculated the incorrect answer, and that was because I assumed deflection angle = I /2 (half the central angle). In the NCEES's solution, it assumes Deflection Angle = I. Any guidance for when I encounter this type of problem on the exam? Is there a "correct" way for calling out deflection angles/central angles?

Edit: Looks like this same questions was asked a while ago, but it' still ambiguous what the deflection angle is

http://engineerboards.com/index.php?/topic/13716-deflection-angles/


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## ptatohed (Apr 17, 2017)

Why is this in the Water subforum? 

LOL, Yes - I remember that linked thread well!    

While it still bothers me, I think it is generally accepted that if you see the term 'Deflection Angle' by itself, it means it is equal to Delta I, or /_\.

In a perfect world, if the term Deflection Angle is used (in the context of Horizontal Curves), there would be more description such as 'The Deflection Angle at the PI between the back and forward tangents', or 'The Deflection Angle at the BC between the back tangent and straight chord'.  But absent any further clarifiers, I think you are too assume the D.A. = I. 

Hey EG, I see you live in Riverside.  I live in Murrieta and work in Moreno Valley.


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## ExhibitGuy (Apr 17, 2017)

Got ya Ptatohed, I figured that's the case. Hopefully a drawing will accompany the question on the test, but I'm not betting on it. I didn't mean to put this in Water Resources haha, just happens to be my depth.

Also nice to see we've got some representation in the I.E . I myself live and work in Riverside.


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