While the Smart car waiting list has been withering, the sub-$20,000 Honda Insight hybrid went on sale in the U.S. this week, as planned. And the newly re-designed Toyota Prius already costs a little less in Japan, in order to compete.

But the big news in cars is the debut of the Tata Nano in India. Like the Model-T Ford in the U.S., the Nano will replace obsolete modes of transportation: feet, animals, and scooters, all of which are inarguably less attractive to a family who needs to get somewhere in a monsoon than a brand-new wheeled conveyance made of metal with a roof and rubber tires.

Ecological advocates have been wringing their hands over the prospect of a projected 350,000 new emissions-spewing Nanos on the road in India—every year. But if the Nano were marketed by Smart, Toyota, Honda, or Ford as an earth-friendly alternative to gas-guzzling family sedans, we'd complain about its rinky-dink looks, but praise its fuel economy and simplicity of design. The Nano's 2-cylinder, 624cc gasoline engine makes 56 mpg. That's more than the Prius and the Smart ForTwo. And at $1985, the Nano costs less than a good road bicycle.

It's also an ecological case study on a massive scale: a teeming nation full of newly middle-class consumers driving modern 2-cylinder cars is arguably better for the planet's future than that same nation driving a hodgepodge of used European and American sedans and SUVs, spewing emissions and chewing up roads. Of course, getting actual Americans and Europeans to relinquish their current cars for tiny eco-boxes is an entirely different problem.

The big, fat elephant in the room of any discussion of green driving in the West is that the only way to effect real change is with a mass changeover to low- or no-emission vehicles. Super-high gas prices is one method to change the game, and the swelling interest in green-driving alternatives that occurred when gas neared five bucks a gallon is proof that the model works. But now that financial incentives have subsided, appealing to customers' sense of style and national pride is a viable alternative—and that's exactly what legendary British car designer Gordon Murray is doing in the U.K.

Murray, the man behind the Maclaren F1 supercar (and the Maclaren Formula 1 racing team), has reinvented himself as the guru behind the T25, a (sort of) top-secret mini-car that he claims will become not only a new British style icon, but an ecological and economical alternative to the hot hatches and "Chelsea tractors" (i.e., SUVs) currently clogging the English roadways. Lightweight, tiny, comfortable for a family of four, gas-sipping and safe—the T25 makes all the same claims as the Tata Nano, but marketed to a different audience. Yes, the T25 will surely be safer and faster than the Nano (and cost more, around $10,000). But the concept is the same: a smaller, lighter vehicle is cheaper to run, better for the environment, and eases road congestion mainly because you can fit 3 of them in the space taken up by a typical SUV.

And despite internet buzz about a possible Ikea car (unveiled on April Fool's Day), the T25 is the first auto to bring some of the Swedish furniture-maker's flat-pack, prefab ethos to automobile manufacturing. Major components of the T25 will essentially be panelized, and therefore easily replaceable; this includes body parts as well as the drivetrain, which means the T25 will be able to run on different kinds of fuels, from gas to batteries to whatever the next affordable, compact green technology may be. It also means that the T25 can be built by non-automobile manufacturers; this week, the T25 was offered to franchisees, and almost none of the twelve interested companies currently make cars.

Of course, the Nano (below) is on the road now, and the T25, as seen above, is just a silver-foil-wrapped promise. But both point to the future of green driving as (1) smaller, (2) simpler, and (3) smarter.