Philip, I wasn't as clear as I meant to be. I was assuming a dead level tunnel and that gravity would then create the illusion it was bent. The Channel Tunnel must go downhill first, then straight then up again into France. Jack Well maybe we still aint as clear as it is meant to be. So lets get things straight.. pun intended. The descent will be just till the road was sure to be under the sea bottom at both ends. We are both ignoring that part of the question, and talking about the level road inbetween these points. You assumed a level road in between these two points. And that assumption is correct.. But you confused your illusions. Any LEVEL road WILL be curved.(bent as you call it). The illusion is that it is straight. Not, "gravity would then create the illusion it was bent" Philip.