[elhigh]

I don't agree that rolling resistance is a bigger issue, though it's pretty obvious that with 18 wheels, there's a heck of a lot more rolling resistance on a truck than a car. Add a full load and it gets worse.

With those big gaps, the enormous open belly with girders and spares and tanks hanging in the breeze, and the bluff nose and tail, the aero of a truck is accurately described as "brick-like," if the brick had a few extra cracks added to it.

My understanding is that rolling resistance increases as a linear progression, but aero is a exponential progression. So the rolling load increases, but not as fast as aero drag does.

Trucks are just about the most inefficient way to get bulk goods from here to there. For distribution inside a city they make great sense, but for anything longer than 200 miles I'd say load it on a train.