Why did the turtle...?

[xallanthia]

I was driving to work this morning and came within a tire's width of driving over a TURTLE in the middle of the road.  It was a big turtle, too--at least as long as my tire is wide!  It was a moderately busy road; I hope he made it across OK!

But seriously, how did a turtle that big...?  This wasn't exactly woodland, although there is a significant creek about half a mile away....