US-based autonomous truck company TuSimple has raised $120m in a Series D financing round led by Chinese tech company Sina.

The startup company will use the funds to increase long haul services for fleets and will work with OEM and Tier1 suppliers to develop commercial self-driving trucks.

TuSimple said that the round was oversubscribed and raised a total of $215m.

The company’s investors include UPS, which owns a minority stake in TuSimple and is currently testing autonomous trucks, Mando Corporation and CDH Investments.

Mando Corporation CFO Jae Chung said: “TuSimple continues to impress the automotive and investor community with its progress towards creating the world’s first commercial self-driving truck solution.

“TuSimple’s technology is at a pivotal point for maturity and it has huge market potential, which is why we wanted to deepen our relationship with TuSimple and become a strategic investor.

TuSimple CFO Cheng Lu said: “It’s highly gratifying to see such strong interest in TuSimple from investors and industry leaders alike, and we are grateful for the support of our committed investors.

“With over 50 trucks on the road worldwide and more than 18 contracted customers, we are excited about the momentum the company has achieved in four short years.

The latest deal values the company at $1bn. With the new funding, TuSimple has now raised a total of $298m.

The minority investment complements the existing commercial relationship between UPS and TuSimple for purchased transportation services.

UPS and TuSimple are currently testing self-driving tractor-trailers in Arizona. As part of the ongoing testing, the goods are being transported on a North American freight forwarding route between Phoenix and Tucson.

TuSimple launched in 2015 and now has operations in China, San Diego and Tucson, US.

The introduction of self-driving trucks aims to increase safety, lower operating costs, optimise fleet logistics and reduce carbon emissions.