Broken-back Curves
Does anyone have any insight they'd like to share concerning the use of broken-back curves? I'm taking a class (Highway Drafting and Route Design), and this type of curve is mentioned.
I'm not sure what a "broken back" curve is, but I assume you mean the short tangent between the two simple curves in your diagram.
My guess for the reasoning is to allow calculation of the delta. If they were compound curves and no delta (included angle) was shown in the drawing, then the curves may not be calculated precisely.
There is similar reasoning for reverse curves.
I have never heard of that nomenclature. Just seems like two curves.
I have never heard that term either. Looks to me as if it is two different curves just separated by a short tangent. See a lot of these at small scale on curb islands often a little half a foot straight line at the bull nose separating the two arcs. If they were together and the radius just changes I would use compound curve. Looks as if the radius in your diagram are parallel but the bearing in to the second and delta could identify that. Just saying you might see that on a test where a corridor two and some parts of each curve are given and one must solve the rest . I am just throwing that out. FYI hint hint.
I've always heard it used, and used, to reference non-tangent curves.
Reaffirmed by Wattles
I heard this term in school, but don't think I've seen one in the wild yet.
Maybe it's just a simple way to avoid a non-tangent curve.
I've always thought it was a common term for two curves spaced very close together but otherwise common curves with nothing else unusual. Much like rear corners of a subdivision being designed to be .30' apart, don't do it unless it is absolutely necessary. Instead of the broken back curves, find a way to make one smooth curve instead.
This is the situation I've heard described as a broken back curve....
I assume the PCC is point of compound curve but based on the diagram it's a lie? 😏
