[GNC] "Travel" vs. "Public Transportation"

[rsbrux]

I just noticed that I have two overlapping expense accounts, "Public
Transportation" and "Travel". I think that both accounts were in the
default GnuCash account tree, but "Public Transportation" is not a sub-
account of "Travel", which is what I would have expected.
We live in Europe and often travel by train and/or bus for both short
distances and on vacation, so I'm not sure where to draw the line
between these two.
What arguments can be made for and against maintaining two such
separate categories?