The cost? The market for these vehicles is incredibly dynamic and flooded with extreme competition, producing prices that range from a high of about $1,000 down to somewhere below $150. It’s easy to find models that cost just under $300—and these come with onboard computers that sync with smartphones so you can listen to music from Bluetooth speakers while you ride. These hoverboards on the market aren’t autonomous, of course, but that can be fixed with some of the technology already shaping the current generation of autonomous cars.
Putting millions of people on cabs and hoverboards would require cleaning up the tunnel walls, adding nice lighting, and replacing the tracks with a smooth, paved road. There will undoubtedly be obstacles. Cleaning up the walls and removing the old track will be difficult and costly. Some of the sections have double tracks that would cost twice as much to remove. Even so, a budget of $8 million for each of the 240 miles in the current system would add up to only $2 billion. Even if that cost were to double, that would still only amount to about one-fifth of the current estimate to repair the existing system. (This is merely an estimate, of course. Anyone who’s followed civic construction knows that it’s not uncommon for estimates like this—or the $19 billion renovation—to have doubled or tripled by the time the work is finished.)
There will be other costs, of course: 240 miles of LED lighting would cost millions of dollars, but installing such a system would have side effects that would make them worth every penny. Rats, after all, hate the light and would be pushed to find new underground homes.
Lighter vehicles would also use dramatically less energy. The current system uses 1.8 billion kilowatt hours to power the nearly 2 billion estimated rides each year. It’s a bit tricky to compare the power that’s running the trains with that of the lightweight boards, but many hoverboards routinely go 15 miles on a battery charge that’s about 15 to 20 percent of a kilowatt hour. In other words, a lightweight board might save 80 percent or more of the power depending on the length of the rides.
The biggest reason is physics and weight. The R-160a subway car, which entered service in 2006, is about 10 feet wide and 60 feet long, and weighs more than 85,000 pounds. The official capacity is about 200 people standing and 56 sitting and, even with the population’s expanding waistbands, more energy is put into accelerating and braking the R-160a car itself than is used to actually move the people. In comparison, it’s easy to find a basic model of hoverboard that weighs anywhere from 18 to 50 pounds, depending on tires and configuration. Think of the energy savings that could result from replacing all of that heavy subway car with 20 pounds of hoverboard—savings that are even more profound in the off-peak hours, when there may be only one person riding on a hefty subway car.