How do you create a map showing every road in the United States, with the precise location of every stop sign, all the lane markings, every exit ramp and every traffic light — and update it in real time as traffic is rerouted around construction and accidents?

That’s a challenge that automakers and technology companies are confronting in their race to develop self-driving cars, the kind that someday will let you sit back and read or watch TV on the way to work each morning.

The need for highly detailed, three-dimensional, computerized maps — which pinpoint a car’s location and understand its surroundings — is often overlooked amid all the hype about autonomous vehicles. The chatter tends to focus more on the various sensors that enable cars to “see” the road and any obstacles in front of them. Those sensors include radar, cameras and a laser-based kind of radar known as lidar.

But digital maps are an equally critical piece of the puzzle.

“If we want to have autonomous cars everywhere, we have to have digital maps everywhere,” said Amnon Shashua, chief technology officer at Mobileye, an Israeli company that makes advanced vision systems for automobiles.