[Bicycle Bob]

Agreed that extreme lightweight techniques are out of place in ordinary transportation, but I still see plenty of reasons to keep the payload above 50%. It reduces rolling friction and highway costs. Rebuilding everything for constant-speed traffic would require more land and more mileage. With regenerative braking, we should be able to keep the loss to 10% per cycle most of the time, and those systems work for grades as well.

If there is new infrastructure to be built, we could have high-speed guideways to keep our passenger pods perfectly safe while we chat and browse. We might merge into trains with mixed freight under robotic control, but with all traffic strictly limited as to weight, so that elevated sections could be built lightly at great savings. Road bridges are built to 100 lbs per sq. ft, and, since pedestrians eventually bunch up to look at things, foot bridges require 120. However, bicycles don't pack, so Dedicated bikeways are safe at 20. Enhanced velomobiles should be about the same.