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.
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.