A way to pack for a road trip with an energetic ASD child is to create a separate tote bag with one change of clothes (for the entire family) for each day of your trip. That way you don't have to load and unload a big, heavy suitcase every day. I also like to pack a pool bag that I can grab quickly, and a small bag of toiletries (shampoo, deoderant, etc.). The pool bag should contain suits, towel, lotions, diaper, deflated/small pool toy, and flip-flops as needed.
Always have a backpack for your child with "busy time" toys, beverage, and at least one change of clothes within easy reach. Also, I like to keep at least two extra pairs of kids' shorts in the seat pocket. I do this for everyday excursions, not just road trips.
Try to keep putting your camera, maps, flashlights, books, and other gear back in the same place every time so you don't waste time looking for them during your trip. In other words, save time by trying to stay organized.
Save your sanity by investing in a portable DVD player. If you don't have one and you will be traveling, look for one during 4th of July, Labor Day, and day-after-Thanksgiving sales this year.