The era of driverless cars is coming down the road.

But not quickly enough for one British man, who ran afoul of the law when he was caught in the front passenger seat of a Tesla set to Autopilot, cruising at about 40 miles per hour with his hands behind his head.

No one was in the driver’s seat.

Witnesses told the police that “traffic was heavy” last May when they saw the nondriver, Bhavesh Patel, 39, of Nottingham, England, in his white Tesla S60 on the M1 motorway near Hemel Hempstead.

The police said in a statement that Mr. Patel, who had owned the car for about five months before the stunt, admitted that what he had done was “silly” but said that the car was capable of something “amazing” and that he was just the “unlucky one who got caught.”

On April 20, Mr. Patel pleaded guilty to dangerous driving, and a court barred him from driving for 18 months.