I've made a small edit to this puzzle to try to make it slightly more difficult; see the edit history for the original version.
The other day, I was taking a driving lesson. My instructor was sitting directly behind me, as usual, while I was driving steadily at about 60 miles per hour.
The instructor told me, "Slow down to 40 miles per hour, and maintain that speed." So I slowed to 40 miles per hour, as she asked, but I found that it was impossible to maintain such a slow speed; I felt a horrible lurching sensation as the vehicle started accelerating again. The instructor said, "You just learned why it's important to keep your speed up!"
Next, the instructor asked, "If we wanted to stop the vehicle right here and now, would that be possible?" As a joke, I replied, "Only if we ran out of fuel!" She laughed.
The instructor then said that actually, we would be able to stop right there and then if we wanted, and she explained how. Of course, if we were to stop using that technique, we wouldn't be stopped for very long.
Anyway, I continued driving along at about 60 miles per hour until the trip reached its natural ending point, and the vehicle stopped. At this point, the vehicle was obviously unusable, so we had it towed back to the garage.
What kind of vehicle was I driving?
Oh, by the way, if it helps, the trip began and ended at a weather station.