Shares in TuSimple, an autonomous truck developer backed by Volkswagen and UPS, fell sharply on Thursday after its IPO, suggesting investors have doubts about the company’s promise to get its technology on the streets by 2024 .

The San Diego-based startup raised more than $ 1 billion in an IPO valued at nearly $ 8.5 billion. The shares traded on the Nasdaq under the symbol TSP at a price of $ 40 each around noon, but quickly fell as much as 19 percent.

TuSimple and other companies working on autonomous vehicles believe that long-haul trucks are particularly suited to self-driving technology. Routes on highways where trucks travel repeatedly are easier to map and pose less of a challenge than local roads where self-driving systems have to deal with unpredictable stop-and-go traffic, pedestrians and cyclists.

TuSimple’s self-driving technology is based on several sensors, but focuses on remote cameras that can map objects with an accuracy of five centimeters and a range of up to 1,000 meters. The company has a fleet of around 70 trucks, 50 of which are in the USA and 20 in Europe and Asia. By the end of March, the company said it had made more than 5,700 reservations for vehicles that typically require a deposit of just $ 500.

The company, which is testing its technology with safety drivers on roads in the Southwest, plans to run fully autonomous motorways by 2024 as part of a partnership with truck manufacturer Navistar. TuSimple has mapped over 3,000 miles of highways and expects the entire 46,000 mile interstate system to be mapped over the next three years.

The competition is heating up. On Thursday, Walmart announced it would invest in Cruise, General Motors’ autonomous vehicle division.