Simple Horizontal Curves
Simple Horizontal Curves
(OP)
Here is a question about simple horizontal curves:
To calculate PC Sta, subtract T from PI Sta, then add L to PC Sta to get PT Sta. My question is, isn't stationing based on the roadway, that is, on the curve? If this is true, how can you subtract T from PI Sta to get PC Sta? The reason I am saying this is because the length of T and length of one half arc are not the same, therefore I am thinking one has to subtract 1/2L from PI Station.
This is assuming that PI is halfway between PC and PT, which should be correct since T's on both sides are equal to each other and the line from center of arc to PI divides the center angle by two.
To calculate PC Sta, subtract T from PI Sta, then add L to PC Sta to get PT Sta. My question is, isn't stationing based on the roadway, that is, on the curve? If this is true, how can you subtract T from PI Sta to get PC Sta? The reason I am saying this is because the length of T and length of one half arc are not the same, therefore I am thinking one has to subtract 1/2L from PI Station.
This is assuming that PI is halfway between PC and PT, which should be correct since T's on both sides are equal to each other and the line from center of arc to PI divides the center angle by two.





RE: Simple Horizontal Curves
1. Stationed along tangents only, not yet stationed along curves; or
2. Dual stationing is being used, and should be somehow identified as such.
I would say that a typical final drawing would be stationed along the centerline alignment only, and the 'tangent' is either given or able to be calculated from other curve parameters.
RE: Simple Horizontal Curves
If that is the case, there are a series of calculations that can be done. However, it is far easier to calculate from the chord or the BC.
If you would like the development of the formula, I can scan it and email to you.
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