I-275 Cincinnati

[amroad17]

I have noticed something interesting about I-275 in the Cincinnati area.  While driving west on I-275 from Kentucky into Indiana, "magic" happens.  On the Carroll Cropper Bridge there are the incremental mileposts up to the Kentucky/Indiana border showing, at that point, mile 14.  Approximately .2 miles further, as you are leaving the bridge, is a small blue Indiana mile marker showing 15 +.19.  Where did the 14th mile go?

It appears to me that mile 14 and mile 15 are the same, which makes I-275 one mile shorter than the 83.7 miles that has been cited on varying web sites.  For those keeping records, this would make the I-435 beltway around Kansas City about 1/2 mile longer, displacing the Cincinnati beltway as the longest in the U.S.

I have no idea how this could have happened.  Maybe it was just a mistake by Indiana as far as calculating mileage from I-71/75 or it may have been a case where the final product ended up different than the original plans.  Of course, before the incremental mileposts were installed, this wasn't as obvious a mistake because you saw mile 13 in Kentucky, crossed the bridge, saw the small 15 +.19 marker in Indiana, then saw mile 16 at the Lawrenceburg exit.  You really did not think about the "missing mile", although I did notice this in 1995.

Just because I happened to notice this does not mean anything has to be changed (mileposts or exit numbers--they have been this way for a few decades).  I would like to know if anyone else who has driven this highway has noticed that this mileage "magic" occurs.

[PurdueBill]

It seems to check out based on the route logs of KY, IN, and OH. 

OH straight-line diagram states 55.48 miles in OH.
IN reference post book states 3.16 miles in IN.  They start their mileposts at 15.00, so there is a "missing" milepost (IN runs 15.00-18.16), but this is absorbed in rounding exit numbers and in the blue 2/10 markers disappearing for a stretch.  Incidentally, Ohio's mileage shows 17.60 at the state line, so that accounts for 0.56 mile that reappears after about a mile "disappears" at about MM 14 where it becomes 15. 
KY route logs show miles 0-13.858 (southern I-75 junction to IN line) and 73.061-83.780 (10.719 miles, OH line to southern I-75 junction) for a total of 24.577 miles in KY. 

The grand total is 83.22 miles according to those; differences in centerline mileage vs. other measurement and how the I-74 overlap is handled may explain a small discrepancy, although most of the subtotals do match up well with more widely published information.