The Sunday New York Times business section included a story on Ford and Volkswagon’s plans to team up to “tackle the self-driving challenge” by using tech from Pittsburgh’s Argo AI. As previously reported, the two companies have invested billions in Argo AI. Their goal is to use self-driving cars in ride-sharing services in “a few urban zones” as soon as 2021.

But as the story by Neal E. Boudette explains, our nation’s automakers and tech firms overestimated the ease with which autonomous vehicles would be able to anticipate and react to human drivers and pedestrians: “A year ago, Detroit and Silicon Valley had visions of putting thousands of self-driving taxis on the road in 2019, ushering in an age of driverless cars,” reports The New York Times. “Most of these cars have yet to arrive — and it is likely to be years before they do.”

The biggest problem? Anticipating human behavior.

“Researchers at Argo say the cars they are testing in Pittsburgh and Miami have to navigate unexpected situations every day,” including bicyclists traveling the wrong way on one-way streets and street sweepers suddenly turning in circles.

So far, they say, “incredible optimism” hasn’t been enough to overcome these challenges.

Read the full story here.