In recent years I've noticed how the shape of long distance busses has evolved. First, the side mirrors, which are no longer fixed to the front corner where they kill airflow down the whole side:
but now hang down farther away, looking like bug antennae:
Next, the rounded front:
and roof extension:
as shown on a Volvo (Elite?).
Finally, (partial) rear wheel skirts, as shown on a Neoplan Starliner:
and on a Man:
The skirts may be more to control spray than for aero reasons, like the
front skirts on city busses.
Unfortunately, busses have been getting taller (=more frontal area) to provide more luggage space. A partial alternative would be a piggyback luggage holder, only shaped like a Kammback
Or an aerotrailer.