This is not good English.
It rejected "A boat trip lasts longer than a car trip", which is certainly as good idiomatic English as "A boat trip lasts longer than one by car".
I used "takes", because in a different sentence, it was accepted!!
could you replace "plus longtemps" with "plus de temps" ?
A boat trip lasts longer than a car trip was rejected
This is not good Australian either We dont use route in this context
"A trip in a boat lasts longer than in a car". What is wrong with that?
I would say that "on a boat," "in a boat," and "by boat" are all acceptable here. Depends what kind of boat you're talking about. You'd never say "on a boat" if you were talking about a dingy.
I wrote "a voyage (=boat trip) lasts longer than a journey by car", but not accepted of course. Reporting.