Hovercraft are, needless to say, noisy, wasteful and don't corner well. Individual hovercraft are also fiendishly difficult bits of engineering. However, simple platforms with seats on aren't. Imagine this then: no more motor vehicles. Instead, there are roads with proximity-activated air jets, above which are partly controlled by the "driver" via signals from the unattached steering column, such that on cornering, the platform is pushed in the direction of the side street. Meanwhile, holes on the sides of the roads suck, keeping the pavements clean and providing a domestic vacuum cleaning service and sticking parked vehicles to the roads by suction, preventing theft.

The roads are paid for by road tax, but the actual price of the vehicles, which are simply platforms with no moving parts, is much lower.

Anyone ejected from the vehicle accidentally will have their impact on the road reduced by the air cushion, and the position of active vents can be monitored by computer to reduce the risk of impact between vehicles and between vehicles and stationary objects. The machinery for the vents can be heavily soundproofed and is in any case subterranean, reducing the noise problem.
-- nineteenthly, May 18 2008

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