I just did a 7.5 hour ride back from Lake Placid, NY, disproving my theory that if you avoid rest stop fast food, you are less likely to become bloated and constipated.

I only experience stoppage when traveling.
In my college years, I would regularly do an 8-9 hour trek (one way) to and from Southwest Virginia in order to come to New York to work and actually make money, twice a month, sometimes more. I would chase down Arby's roast beef with Roy Rogers burgers and McDonald's McNuggets, capping it off with a Bob's Big Boy omelette when I felt somewhat fancy. I can positively attest to not doing number two for up to 3 or 4 days after these Dr. Pepper-fueled night trips, eating Combos and Smartfood while smoking 600 cigarettes and chewing many Slim Jims. It was a true test of colonic capacity.

This time around I made a concious decision to drink plenty of water, minimize the coffee (only one large cup) and eschew carbonated beverages and potato chips. I fasted up until the final hour, breaking down at a fresh popcorn stand outside the last rest stop before the Tappan Zee Bridge. This was relatively fresh food, unprocessed and not something that should have replicated the after-effects of eating a bag of pistachios and 4 pounds of cheddar at once.

26 hours later and I am still waiting.