Standardized ultralight cars with designated roads

The idea of an ultralight car isn't anything new except to implement them with a standardized design with their own road where bikes would be too slow and cars would be too fast and dangerous.

Lots of a car is basically armor to stand up to, ironically, another car's "armor" in the event of a collision. A car's engine is designed to get this heavy armor up to very high speeds and the job of moving the passenger ends up being a small percentage of the equation. Cars also have lots of extra horsepower available for hauling 4 or more people and a trunk full of stuff which is seldom done.

The ultralight standard would allow one or two passenger max and basically be enclosed 3 or 4 wheel motorized bikes. You'd wear a helmet to make up for the fact that it's very lightly protected with perhaps a minimum plastic shell and a metal passenger compartment cage. The most protection would come from two things: the roads being designed to accommodate these and the fact that they would only drive around other very low mass / low speed vehicles. A road with raised sides would also eliminate objects you would crash into. Off-ramps could actually use nets to catch errant vehicles that didn't quite make the turn. Heck, you could even have the walls of the road be some kind of padded netting for that matter as long as it looked good.

The 75 pound 45 mph numbers are just a starting point that you could tweak to get the most efficiency but they'd be cheap, incredibly fuel efficient and the roads you make for these things could be smaller and cheaper than a highway. Since they'd be almost silent you could even put these "ultralight commuter roads" in nicer areas than you'd put a 4 lane highway. Supplement the major commuter routes with these things where possible and you could theoretically cut fuel consumption per passenger mile to way below what any public conveyance like a bus or train could achieve.

When you get to your exit, you switch to "bike speed mode" and use the bike routes to get to your final destination. I wouldn't want these things to start pushing bikes out of their areas so as part of the standardization, the bike speed mode would be enforced in bike areas and an indicator visible from the outside showing that you can't go any faster than the bike speed limit would need to be seen or you'd get a ticket. (A light or little flag or something.) Bikes would have the right of way in these areas.

These ultralights would, by necessity look like little spaceships with their very cool aerodynamic shape. My model would steer with a joystick.