Tesla’s global car sales fell sharply in the second quarter, continuing a decline that began last year, as the company puts a greater emphasis on autonomous driving instead of new models aimed at attracting car buyers.

The company said it delivered 384,000 vehicles from April through June, down from 444,000 a year earlier. Tesla’s limited and aging lineup has not been able to withstand growing competition from relatively young Chinese carmakers like BYD and established Western companies like General Motors, Volkswagen and BMW.

Elon Musk, Tesla’s chief executive, has been seemingly indifferent to slumping vehicle sales, saying that the company’s future lies with technology that will allow Teslas to operate autonomously and function as driverless taxis. Significant numbers of investors have bought into that vision and pushed up Tesla’s stock market valuation to more than $940 billion.

Last month Tesla began a closely watched test of Mr. Musk’s ambition. Specially equipped Model Y sport utility vehicles, which it calls Robotaxis, began offering paid rides to handpicked guests in Austin, Texas.

The guest riders, mostly Tesla enthusiasts with many social media followers, posted almost uniformly glowing reviews online. However, videos they shot betrayed some flaws in the technology, including instances when the cars braked suddenly, dropped off passengers in the middle of intersections, or required intervention from safety monitors who rode in the front passenger seats.

Last week, in another milestone, a Tesla with nobody inside drove itself from the company’s factory in Austin to a customer about half an hour away. “There were no people in the car at all and no remote operators in control at any point. FULLY autonomous!” Mr. Musk wrote on X. Critics noted that videos posted by Tesla showed the car parking at the destination along a curb painted red and marked, “No Parking Fire Lane.”