I posed the following questions to LEEDCoach, and got the responses below.
"Is there guidance anywhere as to how to interpret the Institute of Parking Engineers tables? There are many columns, but none say exactly "baseline ratio", or what it is a ratio of. Parking spaces per peak occupants?
Also, the copy provided for download is of terrible quality and difficult to read. I believe the last column is probably the most important, but it appears that there is text cut off below the last line of what is shown for the "Office Building" Use Category, which I would think would be the most common type of project looking for this information and how to use it.
We're also wondering what a project should do if they have a use category that does not fit into one that is listed in the tables? A common project type we have is a combination of laboratory and office space? What would a project like that do in this case? I have several like this that will be starting soon, and I know the question will come up."
"The Base ratios for parking spaces adapted from the are also listed in LEED v4 Rreference Guide for ID+C, page 79-81, or at web-based credit library: https://www.usgbc.org/node/2613978?view=guide&return=/credits/commercial-interiors/v4#. If the project use is not captured in the base ratio tables or is a combination of uses, your team should select the closest fit at your discretion and provide a narrative justifying the selection in project documentation."
I don't think their response was particularly helpful (nor do I think they really answered the questions submitted), but this is what has been provided so far. I'd recommend that each of you also reach out to LEEDCoach or GBCI with specific questions. Maybe if they keep getting the same question, they'll post an addendum to clarify.
Please post here if you get any additional information!