bumpiness

Given the bumpiness of the road ahead, you might be better off with a crash helmet.

考虑到你面前这条颠簸路，你最好还是配个头盔吧。

So the bumpiness, the rising high altitude, and the long duration of these two things made this short distance of the road the toughest.

崎岖平路，逐步升高海拔，和很长持续时间使这路成为了最艰难一。