In the latest episode of Crazy/Genius, produced by Kasia Mychajlowycz and Patricia Yacob, we talk to experts about how autonomous vehicles might change the world. People tend to predict the future by analogy, and so self-driving cars’ potential has been compared to a smartphone, an elevator, and an autopilot. But after speaking to several technologists, urban planning experts, and historians for this episode, I’ve come to the conclusion that the best metaphor for the self-driving car is a 20th century technology so subtle, almost invisible, you probably forgot that it had to be invented in the first place.

The self-driving car is a highway.

From a distance, car culture looks like a cavalcade of waste.

First, it requires an extraordinary sacrifice of life. Approximately 1.2 million people die every year due to automobile accidents around the world. In the U.S. alone more than 30,000 people die from cars, making it the leading cause of death for people under 35. “This is insane,” Dmitri Dolgov, Waymo’s head of technology, told me. “Our cars, they don't get distracted, they don't get tired, they don't fall asleep, and they don't drive while drunk.”

Second, consider the wasted space in cities. Before the 1920s, most urban residents commuted to work using public transportation. Today, eight in 10 Americans drive to work; just 5 percent still take public transit. The vast majority of commuters drive alone, despite occupying a big metal box designed to hold a medium-sized family. In the space taken up by a typical car with one driver on a highway, rail transit can fit 25 people.

Finally, there is the wasted investment: Americans spend tens of thousands of dollars on a car—more than any asset besides a home, on average—but leave the machine idle for 95 percent of its lifespan. As the automobile is the mechanical equivalent of a sloth, it only follows that it would need ample room to nap. In cities like Philadelphia and Seattle, there are four parking spaces for every household, requiring gaping cavities of concrete in some of the most valuable real estate in the country.

“The automobile has been pretty much the same ever since it was invented in the late 1880s by Karl Benz,” Lawrence Burns, a former GM executive and author of the new book Autonomy, told me. “It is really messed up! But that's the way it's been for over 130 years.”

Burns has a bold vision of the future, where just about everything about the car’s relationship to the consumer will change. Instead of buying cars to keep in their garage, more riders will choose to subscribe to trusty autonomous fleets (like a taxi service or Uber, but cheap, electric, and driverless). For more than 100 years, car companies built driver-centric machines. But self-driving cars will be designed around passengers—consumers—and that means they don’t have to be what we consider “cars” at all. Imagine a coffee shop on wheels, that drives you to your doctor’s office. Or a comfy hotel bed that drives you to your in-laws for Thanksgiving. Or an Amazon store carrying household staples that roams a downtown area, waiting to be hailed to an apartment.