Catapult Plates for Cars Voting: 0
Making cars get a glide over medium distances.
So building a bridge is a massive infrastructure undertaking. Can we do something more fun? Physics of cannon balls and gliding is well known, and we have the math right for control of gliding, and light propulsion engines.
The "Catapult Plates for Cars" would work by using your car's momentum as the initial energy, magnetically locking and clamping your car to the plate, and then using the rail-gun technology to accelerate it to the speed of say over 500 mph over a short distance, so that relatively small wings on the sides of the plate would be enough for your car to fly over a distance without road (such as a mountain range, a large crevice, or just about any two places of the city).
Your car would take a near-quadratic equation trajectory to reach the destination, every time feeling near-0G experiences in the midst of it.
The plate would have mini liquid fuel rocket engines to adjust the glide to precision-align with the plate capturing end, which would decelerate by recuperating the kinetic energy to some large high capacity condensers, to be used for another ride towards the opposite direction.
To avoid the in-air collisions, the mini rocket engines would be used as well, allowing for a controlled in-air car flows between two points of a city.
Slash the road infrastructure development costs by large margins. And, can't see how this wouldn't work for capsules with individual humans too -- think "Glide-Lifts." Could be closest thing to teleportation, and a direct application of projectile control technology.