This tour is indeed "an amazing, amazing trip" and given the opportunity to go, one you shouldn't miss! I took this tour two years ago and don't remember any twisty roads, overly long bus rides or any of the tour members mentioning feeling nauseated from the bus rides. My sister was with us and she is one of the first to feel the effects of twisting and windy roads. I would mention this to your guide at your initial meet and greet. He or she will certainly help you out and one thing I have found to be true is that riding more towards the middle of the bus will be your smoothest ride. My sister swears it's true, as do others I have talked to. I would try to sit right across from the "second" door, right in the middle of the bus. Given that possibly the itinerary has changed since I took the tour, you might give the tour office a call as ask one of the charming men or women who work there. They are all beyond helpful, understanding and probably have heard this question before.