Sometimes ya just gotta bite the bullet and do it. When I was a kid I had a mother who wouldn't allow me to go swimming until I could swim. Great thinking! But you're in the same boat. You won't learn to drive on the highway until you try.
If your fear is only lack of experience it will go away quickly. If it's a genuine phobia (like acrophobia or claustrophobia) that's another matter and you might need professional help, perhaps from a hypnotherapist.