Originally Posted by
AlmostTrick
I agree! But I think more weight is always going to require more power to keep it moving, even on a flat rail. As I understand it the math you presented (thank you!) agrees.
So getting back to the OP's question, yes, weight does matter, even on a flat road.
Yep we're always going to have rolling resistance, no getting around that. How much weight matters to that (proportional to total weight) is apparently hotly disputed.
Regarding the effort involved with the change in momentum to accelerate, it would seem energetically balanced with the extra momentum when decelerating provided you keep off the brakes. Although the metabolic efficiency (and cumulative fatigue from numerous accelerations) comes into question, you don't get that part back.