DEARBORN, Mich. — Raj Nair, the development chief leading Ford Motor’s effort to build self-driving cars, concedes that he does not know what caused the fatal May accident in which the driver of a Tesla Model S sedan, operating in Autopilot mode, crashed into a tractor-trailer crossing a roadway in Florida.

But Mr. Nair has given considerable thought to the circumstances — a truck turning left into traffic and a partially automated vehicle traveling at highway speed, leaving little room for miscalculation. He has pictured the car’s camera looking ahead and struggling to make out a white truck against an overcast sky, its forward-looking radar beam possibly shooting under the truck’s trailer.

The conclusion he has drawn: The current state of even semiautonomous driving technology isn’t quite ready to take on such a complex traffic situation. That is why Ford, which on Monday demonstrated its own approach to self-driving vehicles, said it was convinced by its decade of research to take a go-slow approach.

“We’ve not been able to do that with cameras and radar,” Mr. Nair said of Autopilot. “Not to the safety level we would be comfortable for introducing that into production.”