ADA Curb Ramp Workflow

[Anonymous]

My current workflow for creating curb ramp designs feels a bit dated. I'm curious how others are doing it, hoping to steal some knowledge. Let me say that we're using C3D 2015, about to upgrade to 2019, so we're obviously missing out on some new features.

So here's the jist of what I do: I create an alignment at the gutter flow line, extending 5' past the curb return in both directions to sample any relevant surfaces (I don't necessarily like this - having an alignment start artificially early just to sample surfaces, makes it confusing on plan) to get an idea of incoming and outgoing gutter grades. 

I then create two profiles, one for gutter flow line (FL) and one for top of curb (TC), run a custom assembly on the FL targeting the TC profile with the curb face to adjust curb reveal. This step is part of my workflow because in the past (working in development) I was required to show these profiles on plan. Now I'm not, so I'm debating whether or not feature lines would suffice here. 

Assuming the horizontal line work is already drawn, I copy in those lines and convert them to feature lines to define the sidewalk ramp leading up and out behind the curb. Historically, I would enter feature line elevations where they attach to the corridor at the back of curb manually every time the FL profile changes. Now, if I were going to stick with this workflow, I'd probably extract a dynamic feature line from the corridor at the back of curb and make sure it's in the same site as the feature lines defining the sidewalk portion. Especially with the new feature line priority tools, this should in theory work well and reduce the margin for error.

Finally, I would create a surface (single surface - add feature lines to corridor surface - as to allow triangulation between feature lines and corridor), data shortcut it out and label that for my plans.

This workflow was developed for new construction development, for use in something like a subdivision, where the entire project could be a single corridor model. Now, I have no requirement to show profiles on plan, and many projects are simply curb ramp replacement projects so this workflow seems like overkill.

A few options I'm considering are: feature lines defining the new curb FL and TC instead of corridor, and labeling feature lines directly instead of the surface. This would require the design elements (feature lines) be in the same DWG as the layouts, or at least XREF'd in. Neither of which are currently part of our standard workflow.

To wrap it up, I give spot elevations at all locations and northing/easting table for the FL alignment. This should give a contractor enough to build these things to ADA standards (assuming I didn't leave anything out of this write up) though I argue that we give them too much information with all of the spot elevations - grades should suffice and accommodate construction tolerances.

Sorry for the long winded description but I want you all to pick my workflow apart, and have a hearty discussion on how to approach these things in various design scenarios. What do you guys do to get these designs out to bid, and what new tools do you use to make these designs easier (dynamically linked feature lines, feature line prioritization)?

[jeff_rivers]

I haven't done any ADA ramps for a while now, but my workflow is quite similar to yours.  Alignment along the flowline, create a FG profile & profile view, then use featurelines and profiles to model the ramp.  I set the flowline alignment to a no display style, then create a featureline right on top of it that duplicates the alignment's horizontal data and the profile's vertical data.  

I do use the site & featureline priority tools to organize the featurelines; the flowline featureline is the highest priority, no other edit to any featureline will affect it.  Next highest priority are the featurelines that define the ramp & landing, no lesser priority featureline can affect them.  Finally a couple featurelines on the existing sidewalks where I think the new work will tie in to the existing.  These also are set to the highest priority (obviously I don't want to accidentally edit the FL elevations representing the existing work).

For parallel ramps I do most of the work in the profile view.  I also project featurelines into the profile view as needed, especially for complex combination ramps, so I can see what's going on (see the image below for a complex combination ramp).  The critical part for a combination ramp is the profile along the back of walk, to get the outer ramps, the landings, and the inner connecting piece of sidewalk to all be compliant.  It's easiest to model this as a profile, using the profile geometry editor. 

I use the bare minimum of featurelines to model the ramp, I used to go into detail for all the pieces of the flares, or the ped curbs, and so on, but the workload and complexity go up exponentially (see the image below for a complex combination ramp).  I don't model the actual depressed curb in all cases.  

Next I create a small FG surface for the ramp(s), out to where the new work ties in to existing, and I label the grades and dimensions.  Then by editing the profiles and featurelines I can see the effect on the surface.  I'll have my workspace split into three viewports:  Profile view, plan view showing only featurelines, and an isometric view with the surface on to get an overall view of what's going on (that's a tip from Jeff Bartels and his Civil 3D Immersion blog).  

We put a lot of thought and discussion into what to show on our plans, and determined that we will only show proposed grades, and except for flowline elevations at the quarter-deltas we will not show any other elevation information.  The contractors get all the slope information they need from the slope labels, and it's up to them to set their forms accordingly.  We do not stake any elevations other than along the flowline.  

I work in a primitive drawing that is xref'd into the production plan, and I use a label style that displays on the final plan.  Generally the views are 1:5 scale so the plans are easy to read (our normal road & paving plans are 1:20).  

I also created a custom label for featurelines that labels grade (%) and distance.  This is handy because of the 15-foot rule (if a ramp graded to 8.3% does not catch in 15 feet, the ramp may be made steeper in order to catch within 15 feet).

Finally we decided that all ramps are to be designed to a maximum grade of 7.5%, not the ADA max of 8.33%, and all landings are to be designed to 1.5%, not 2.0%.  Our state DOT also recommends this approach.  

Some time back I built a spreadsheet to do a bunch of specific calculations for me.  For example, given two station/elevation points, it calculates the grade between them, given a station & a grade, it calculates the resulting elevation at a distance, etc.  It has about eight or ten specific calculators on it, but I don't use it very often any more. 

We bid our curb ramps as square feet of concrete, just like sidewalks, whereas some other agencies bid them per each.  Our way allows the contractor to make modifications as needed to fit actual site conditions and get paid for any extra concrete required.  Our overlay program does 50 to 200 ramps per year, and we've not had problems with this.  

Attached is a detail from a consultant-prepared plan done to our requirements.  It's a little cluttered, but there is enough information for the contractor to build the ramps, and also the contractor will understand where the ramp will be non-compliant due to existing site conditions ("Built to the maximum extent feasible").  

One other thing we do is if we are upgrading ramps at a signalized intersection, we run empty conduit from the nearest signal junction box to a 12" x 12" knockout panel located where the future APS pushbuttons need to go.  Typically we upgrade ramps during one season, then upgrade the signal pushbuttons the next season, using different funding sources.  We've done several intersections this way and it's worked very well.  The signal contractor removes the knockout panel, installs the foundation for the pushbutton post, and connects the APS wiring to the controller using the new conduit.  

[Anonymous]

Jeff, thanks for the thought-out response. Your experiences and workflows actually mirror my own pretty well. It sounds like, despite your use of profiles for design, you largely utilize feature lines as your medium. Am I right? It seems that labeling feature lines, as opposed to a surface, will accurately depict the design intent without the finicking and fussing that I've encountered with surface labels (really not too bad).

I appreciate the attached image and am working on convincing everybody here that showing only grades behind the curb is the way to go. I like the idea of pre-installing conduit for push-buttons, though we typically replace them at time of ramp upgrade (though these types of things are in flux, as this is the first year that we're re-doing curb ramps in advance for our resurfacing program). I also think that bidding the walks as a SF instead of an each item is ideal, given the capacity for change in field-fit applications.

[jeff_rivers]

Yes, I discovered featurelines, sites, and the hierarchy of priorities all about the same time, when I had a large overlay/ADA ramp project to cut my teeth on.  I will have to try labeling just the featurelines next time, as labeling the surface is sometimes problematic.  

You may find this helpful too; our ADA coordination team put together this document that covers some of the design information that's not in the ADA law nor in the PROWAG documents: 

https://snohomishcountywa.gov/DocumentCenter/View/12189/ADA-Decision-Matrix?bidId=