Route A ends at route B, and vice-versa.

[roadman65]

Port Orange FL has both FL A1A and FL 421 end at each other at US 1.

One could say now both FL 417 and FL 429 end at each other now that the Orlando Beltway is completed.

[pderocco]

In Gloucester MA, route 127 ends at a rotary with route 128, and then a few miles up 128 crosses 127 and ends a block later at 127A. The interesting thing is that 127 goes way up into Rockport and does a big loop before coming back down to end at 128. Very scenic ride.