Sorry for the delay in my reply and I'm not sure I'm going to be much help here.
I disagree with your interpretation of the message you received from the D.O.T.. It by no means states that the sign is incorrect, the engineer simply comments on the fact that a signal head was moved but the sign was not moved with it. PERIOD. No indication of any sort that it is in any way incorrect or even questionable. In fact, if it were incorrect, there would be no need to conduct and engineering evaluation to determine its validity or lack thereof. Quite frankly, and when it comes to the specific area where the right turn signal head is located, I find myself looking at two current pictures (picture 2 of 3 and picture 3 of 3) yet the signal heads look out of order.
For starters, most states have a manual which in part or in whole is based upon the Federal MUTCD (Manual on Uniform Traffic Control Devices) issued by the U.S. FHWA and
while there is in fact a manual that is used in Iowa, the section that is dedicated to signs and signals if fairly limited. So basically, you're starting out at a deficit in that you do not have any specific direction on where such a sign should be placed.
However, I think a case could be made that if there is any reference that should be followed, it should be the federal standard and for that, and since the reference date for this installation is June of 2010, then the MUTCD version published just prior to that would be the
December 2009 version of the federal MUTCD which you could find HERE. (Careful as it is a HUGE PDF document). If you are able to download it, then I refer you to section 2B.54 starting on page 95 and ending with page 97 and it shows the following:
As you can see there are several possible scenarios and I highlighted the one that is relevant to your situation on page 95 in red rectangles. I do believe that they are in fact using the correct "R10-11" sign, (see page 96 second row, first sign on the left) and the guidance for its use, simply states:
[QUOTEDec 2009 Federal MUTCD - Section 2B.54]"If used, the 'No Turn On Red' sign should be installed near the appropriate signal head."
Bookmarks