roadway centerline question

[nostupidquestions]

we're doing a widening/resurfacing project. the roadway centerline meanders quite a bit such that i can't get nice long tangents and curves for my alignment, just short segments. my profile needs to be at the actual centerline of the road to be accurate for the profile and cross sections but there's no way i could use this alignment for a geometry plan. i can make an arbitrary baseline alignment for construction layout purposes, say one of the r/w lines, but i'm not sure how that works. both alignments would start at 10+00 but they won't end at the same station. if i use the baseline alignment to set structures, they may not line up with the stationing i used for my actual centerline of the road.

[mathewkol]

Attach an image that shows the existing and the design.

[nostupidquestions]

i would but my road is over 5 miles long. my existing alignment follows the centerline points the surveyor shot so it meanders. i don't have a proposed alignment yet.

[mathewkol]

Ok then. Not sure how we can help without seeing something.

[owenmull]

So, you dont have the original record plans for the highway from your state's DOT? You developed the existing CL alignment from field survey data, I'm assuming, and you want to makea simple (geometrically, anyway) alignment that matches the existing so when you create new sections, etc. the stationing matches. Am I correct so far?

If you are using survey data for your existing CL, then there really isnt a heck of a lot you can do, other than just using judgement, and editing the horizontal geometry by hand, and doing it that way, you're only going to be so close.

Of course, in an ideal world, you could take your DOT's plan (Im assuming its your DOT, but whoever holds the record plansets) and recreate their alignment and plop that into your survey data from the field, but it is a less than ideal world in which we live.

Maybe somebody has an idea here, but I would say that without the original record plans, it's a little different.

[owenmull]

I would say, that in the absence of any original plans, and if this isn't a highway, just a gravel/county road, that you may just have to re-establish an alignment yourself, use the survey data to give you ideas for curve radii, lengths, etc. but it appears to me you have nothing concrete to go off of.

[nostupidquestions]

as far as we can tell there is no described alignment for this road. it's a r/w by maintenance from what we can gather. the r/w is all over the place. i'm trying to put in an alignment that best fits the existing centerline without there being a bunch of 100' tangents. i have seen plans where the baseline is not anywhere close to the centerline. i just don't understand how you can give stations and offsets based on a baseline when you have a profile based on the centerline of the road.if it was new construction it would be easy but it's milling and widening so we have to keep the original centerline and work from there.

[mathewkol]

Your corridor can have one alignment that follows the surveyed road CL and you can make another alignment that is a best fit that you show on the plans.

[sboon]

OK - let's back up to the original problem.  You said that your alignment and profile needs to follow the existing because it's a milling and widening.  I don't understand why you would assume that.  I've designed a fair amount of roadway using similar scenario and I only used the existing centerline as a reference to get started from.  My design centerline almost always changes to smooth out any minor wiggles or to clean up weird curves etc.

[nostupidquestions]

i'm not assuming. that's what they want. i made the mistake of trying to fix things like that on the last job and i had to go back and redo it the way they wanted it.

[sboon]

Fair enough - some people want what they want, right or wrong.

This is a case where the methods used to build the assembly can drive how the alignment and profile are built.  The MillAndOverlay sub is not going to use a design profile, it only builds from the attachment point and existing crossfall.  That's why I'm questioning your need to match existing centerline profile.  Which subassemblies are you using to build the design?

[nostupidquestions]

doing it right would have made life so much easier but i get paid by the hour so whaterver they want.

i needed a design profile for the band elevations, not for the corridor. the existing centerline profile follows the crown of the road. like you said, the mill & overlay hooks up with the attachment point (the crown of the road) and existing eop. i used the mill & overlay and the mill, level & widen subassemblies.

[sboon]

If you have an existing alignment and profile on the old centerline then you can superimpose that profile onto your new alignment and label that in the band.  You should also be able to insert a generic link into the assembly, to shift from the new alignment over to the old one before it starts building the new roadway.  That way your design follows a nice straight and smooth baseline but still uses the old crown for reference.