Most modes of transport humans have devised are capable of going up inclines. Cars routinely handle 30 degree inclines. Humans ourselves can handle extremely steep inclines around 80 degrees (especially when using stairs or steeper when using climbing gear). But trains have a huge problem handling inclines; the hardest incline in England (the Lickey Incline) is just over 1.5 degrees, and to get a train up that requires adding "banking locomotives" (additional engines in the back, to push).

This is one of those questions I never thought to ask. I've been on lots of trains, but that travel has, in retrospect, been extremely level compared with all the car and bus trips I've taken. If you're curious why this is, let Top Gear co-presenter James May explain why trains are built for level travel, and supremely ill-suited to inclines (and declines!).

If you're curious about the math of how a car goes up an incline, this discussion thread might interest you.

If you'd like some more James May material on trains, check out these outtakes from the above: