Ivor The Engine wrote

to be discontinuous. In the US (and I think in many parts of
Europe?)
the common section bears multiple designations.

Yes, but the point being made is that combined roads in the US also
keep their N/S or E/W designations regardless of true compass
bearing.

We don't append the direction to our road numbers, just provide
generic 'The NORTH' or 'The SOUTH', etc. directions at certain
junctions.

There have been suggestions, however, to change signage so it's the A1
and A5 North & West but the 1A and the 5A South and East.

And, I suppose, the M25 clockwise but the 25M widdershins.

--
Mike D