Dave S writes:

Is that a US only rule or universal? They refer to lots of lower
altitudes as flight levels over there in Europe where mx is..

The rules vary elsewhere, but I "fly" only in the United States, since I know
the regulations there better, and they don't change every 300 miles, and I'm
more familiar with regions in the U.S.

The rules in France are stranger, and they change from country to country, and
Europe in general is very messy in this respect, so I just don't "fly" there.

If I were ever to get a pilot's license, it would be in the U.S. Since I
don't live in the U.S., that's one reason why I don't try to get a pilot's
license (but it's not the most important reason).

Anyway, back to the topic ... it's true that I can fly in the general
direction of a road instead of following it precisely, but I find that it's
easy to get so far away that it's hard to see the road any more. Some
Interstates will turn west for miles, and then turn east again, and so on.
They stay in one direction long enough to get away from you if you are trying
to keep an "average" heading, but if you turn you have to change altitude.
Climbing and descending 2000 feet every few minutes seems like a lot for a
small aircraft.

I haven't seen anything in the FARs that provides a way around this for cruise
flight, except, as Bob has pointed out, flying below 3000 AGL. That would
work well enough in Iowa, and then the problem is solved. But over hilly
terrain it gets more difficult, and also other rules come into play for
low-altitude flight, such as the need to respect limitations over congested
areas, wildlife preserves, etc.

So, I am open to suggestions, and I'd like to hear how other pilots (real or
virtual) deal with this.