Frost heaves. Pray you never have 'em. They're not what you think, but are caused by the permafrost under the roadbed melting slightly and then refreezing. If you drive such a road at the wrong speed the frost heaves can cause you to heave -- and even damage your vehicle.

(I guess I forgot to mention my companion, A Lady Known As Lou. And other things. She was cheaper than an electric blanket, anyway.)