jen, you are not alone -- I have driven with folks who have the same fear. And my wife has a similar fear when we are hiking on the edge of a cliff.
Other than planning a flatter route, you can do what my wife does when we are in a cliffy spot -- look down, look to the side, anything but looking at the edge. I assume you've tried that, right??
And welcome to the forum -- please disregard the folks who (for some unknown reason) like to say discouraging things. Some of the folks who participate on this site will provide you with useful info. Some won't.
