I had a bunch of geewiz ideas as a kid, but I forgot most of them. Here's one, though:
I used to look at the huge (this was in the mid 80s, my dad worked on all sorts of relatively extensive electronics hardware, and I was small) boards and cases abristle with components that my father used to bring home from work. To me they looked like miniature cities, water tower capacitors, integrated circuit factories, high speed highway and railroad paths crisscrossing everywhere through those urban landscapes, etc.. I'd spend hours looking at them in awe at the endless permutations. It got me thinking that highways as we have them could be a lot more efficient and a lot cooler if we made a few changes:
Cars could ride on common magnetic pulses the same way electrons ride the current in those circuit printed paths. Cars would ride up to the highways on their own power, but fall in line the once there.
It'd reduce accidents from human error, and would probably also improve mechanical failures' aftermath, considering all cars would have near-zero relative velocities.. e.g. There could be some scheme for cars to un-float back down into guiding rails if power was interrupted.
Traffic flow could be decentralized among all cars rather than slaved to a single controller, without much fuss if they all operated on a same standardized protocol for passing, exiting etc.
The real problem, which I only thought of a few years later, was how to power all this. It can't be worthwhile if for all its practicality, it costs more than the present solution + the cost of switch-over. The solution is pretty simple, maybe even without much more superconductive tech than we have now: space power.
At present (as far as I can tell), the biggest drawback to space beamed solar power is the risk of being on the receiving end of all that power.
A simple enough solution is that, such highways being most interesting in long-distance applications, they'd easily have free room somewhere along their paths (a little off from the highway itself, most probably) to accomodate power beams away from any population or vulnerable infrastructure.
In any case, a large part of any damage can be prevented by just turning off, or diverting the earthbound power beam anytime it'd diverge from its target down on the ground.