By Joann Muller

After years of development, autonomous trucks are gaining traction across the Sunbelt, but the industry's next breakthrough is economic, not technical.

Why it matters: Large-scale adoption won't happen until driverless trucks become cheaper to operate than human-driven ones — an inflection point that could soon reshape freight logistics, labor and supply chains.

State of play: Goldman Sachs Research expects autonomous trucks to become cheaper per mile than human-driven trucks in 2028.

• One AV company, Bot Auto, says its trucks are already cheaper than a human driver, at least on one route from Houston to Dallas.

The big picture: While robotaxis get most of the attention, autonomous trucking could be a bigger business.

• In 2035, the global market for autonomous trucking will eclipse that of self-driving cabs — $560 billion vs. $415 billion — Goldman predicts.

• In the U.S., the AV trucking market is projected to grow from $16 billion in 2030 to $105 billion in 2035.

The economics are shifting quickly, researchers say.

• A regular class 8 semi-truck — the tractor, but not the trailer — costs about $200,000.

• Autonomous technology — computers, sensors and software — adds roughly $125,000 to $150,000.

• By 2035, those costs could fall to roughly $35,000 to $40,000 as hardware costs improve and production scales up, per Goldman's forecast.

Between the lines: For shipping companies, all that matters is lowering the total cost of operation, typically measured as cost per mile.

• Costs include everything from monthly truck payments and insurance to fuel, maintenance, driver wages and tolls.

Zoom in: A human-driven truck today costs about $2.26 per mile on average, according to the American Transportation Research Institute.

• An AV truck costs around $8.60 per mile today, per Goldman.

• By 2035, however, the AV truck could cost as little as $2 per mile, the researchers project.

AV trucks have another advantage, too: They can drive all night, while human drivers are required to rest after 11 hours behind the wheel.

The latest: Xiaodi Hou has been obsessed with cost-per-mile since founding Bot Auto in 2023, after his previous AV trucking company, TuSimple, shuttered its U.S. operations and moved to China.

• Bot delivered its first commercial load without a safety driver onboard last week for Ryan Transportation, a freight broker.

• It's just one route, a 230-mile stretch between Houston and Dallas, but the math is encouraging, Hou, Bot's chief executive, said.

By the numbers: While the ordinary human-driven truck would cost $2.26 per mile to make the delivery, Bot's driverless truck completed the trip for $1.89 per mile — and collected revenue for the shipment that's equivalent to $2.70 per mile.

• "We're reaching the tipping point where we can make money," Hou told Axios.

Reality check: The road ahead still has some bumps. Autonomous trucking companies still have to prove their rigs are safe for U.S. highways.

• There are no special rules for autonomous trucks, so operators are self-certifying their safety.

• Labor unions argue the technology will destroy jobs and isn't ready for prime time.

What we're watching: California just approved new rules clearing the way for AV trucks in that huge freight market, overcoming labor objections.

• Congress, meanwhile, could write clearer rules for the industry later this year when it renews a major highway funding bill.

The bottom line: After years of delays, autonomous trucking may finally be on the verge of a breakthrough, including beating human drivers on cost.