Elon Musk has dropped his latest vision on us — a future in which we avoid "soul-destroying" traffic by vanishing underground in our electric, self-driving cars, and tool through our cities within subterranean tunnels, only to pop out at our destination on the surface. Musk says such tunnels will be necessary, namely because we are about to see a massive increase in the number of cars on the road.

Not so fast: A professor at Carnegie Mellon University is pouring cold water on the idea, at least for now. Costa Samaras, informed by his work on the mile-long extension of New York's No. 7 subway line in the mid-2000s, suggests that technologists already have enough on their hands optimizing fully autonomous cars; it's getting way ahead of themselves to contemplate yet another ultra-complex concept. He told me:

Maybe let's figure out shared, fully-driverless, electric mobility first?

Video and more 197 words

Here's a video that Musk played while speaking on stage with TED's Chris Anderson on April 28.