Right now, ODOT is rebuilding I-270 on the southwest side of Columbus, between approximately mileposts 2 and 9. They aren't adding capacity, but there will be inside breakdown lanes on I-270 where there were none fefore. (I had hoped they would at least make the bridges wide enough for a future extra lane, but they're apparently not doing that.) I have, however, noticed that they appear to be realigning the ramp from 270 SB to 70 WB, making one smooth curve instead of two curves with a straightaway between. This was not mentioned in any of the public materials for the project. I don't know yet if other changes, perhaps to lane configurations, might be left after the project is done.
Also, back in '07, ODOT quietly (and probably in just one night) eliminated the "inside lanes merge" condition where the ramp from I-670 EB meets I-71 SB. They did so by having the right lane of the ramp end just before reaching I-71. I don't think there were any announcements of the change, though it was a minor one.
Anyone else have examples of changes that DOTs have done "under the radar"?