Computing the optimal road trip across the U.S

9.33 days worth of driving time -- that's a fair bit!

You'll want to do this in a car. Some of the cities and routes will not allow an RV. For example, Washington DC and NYC don't allow RVs on their streets (just too congested for a 45 foot Class A, with or without a towed car). Getting into NYC in an RV would be difficult anyway, as the Port Authority doesn't allow them through the tunnels because of the on-board propane commonly carried.