I know that the property has been damaged, but by how much?
Uh... ya got any got sales in BOTH before and after conditions to PROVE it?
Lots of businesses survive on RI-RO modifications... since that usually only happens when a property gets a higher traffic count to go along with it! I am not saying I wouldn't squeal like a stuck pig if I was apprised of that modification to MY properties entrance(s)...
However: You may want to read through this link-
City of Wichita V McDonald'sand then ASK the legal department of the state in which you are doing the work what the LAW is in THAT state regarding circuity of travel
in that state - A FOIA request will work for non DOT employees - employees should go through channels. And then your next step should be to... ask a second opinion of someone who is NOT involved with the DOT...
It is merely a coincidence that it was MickeyD's which was involved in this case - I didn't post it for that reason... Happens it is one of the best and most recent and CLEAR rulings on the subject of circuity of travel - and I am not sure which states are citing it as the source for further decisions, hence suggestion #1. I learned about it in a national organization course, where it was conveyed that this is the precedent setting case on the matter - subsequently cited as case-law by other entities. Which 'precedent' is often cheerfully ignored by most courts when dealing with condemnation. So good luck with that part of it...
Short story is that cutting off direct Highway access, if access remains via public roadway is NOT the problem of the condemnor... as far as damages based on altered access ALONE are concerned. If the H&BU remains the same <shrug> you appraise at H&BU.
So cutting off one way of in-out AND retaining at least only ONE in-out from the same location AND not altering the other in-out? <shrug>
Mickey D's is probably FULLY aware of this case...

Your State DOT may not be... Have fun!
And remember no matter WHO your client is you area Disinterested Third Party...
who may never work in that town again (HA!)