Where realignments are useless.

[roadman65]

https://goo.gl/maps/Cf55efnyL4ceCf5X7
DelDOT a few years back realigned Route 896 to bypass the University of Delaware using both Christiana Parkway and Elkton Road instead of using College Avenue through Newark, DE.

https://goo.gl/maps/ixXYtqctzpnPZ7R17

However with phone apps and on line maps, the host ignores the reroute for the old route as in the aforementioned link above.

Notice how it ignores DE 896s alignment change completely north of DE 4 and south of DE 273?

[Max Rockatansky]

The realignment of CA 111 out of downtown Palm Springs is nominal as a through route.  It still is often easier just to go through downtown despite the newer pedestrian features than Vista Chino and Gene Autry Trail.  I'm not sure why Palm Springs just didn't come to some sort of full relinquishment agreement in their city limits.

[SkyPesos]

Most of Indiana's realignments and truncations.

[Great Lakes Roads]

Most of Indiana's realignments and truncations.

I second that! 

[wanderer2575]

The rerouting of M-43 to run concurrent with M-89 between Plainwell and Richland after the road through Kalamazoo was turned back to the city (in Michigan, US- and M- routes do not run on city-owned streets).  I get the desire to not assign a new number to the segment either east or west of Kalamazoo, but nobody is going to be following this new M-43 thru routing.  Westbound, M-43 actually runs south from Hastings to Richland, now northwest with M-89 to Plainwell, then south again with US-131 back to West Main Street.  Vicee-verse for eastbound M-43.

[Ned Weasel]

US 40 in Lawrence, Kansas

Also US 169 in Kansas--  Wait, I'm not sure if that's ever been useful between the point where it meets I-35 in Olathe, and downtown KCMO.