Direct, fast, and as safe as you want to make it, with all the usual caveats about good weather and road conditions, take it easy, be sane, etc. Your small car will be fine on any interstate (and in my opinion, on ANY road in the US). The interstates are made for fast movement, and the grades are mild by design. I drove little cars for years, including an MG-B on road trips, albeit short ones. Not the smallest car in the world, but purty littel. WORST problem was I kept getting caught on the bell rope in the Jack-in-the-Box Drive-Thru. :)