The self-driving freight truck startup TuSimple has been carrying mail across the state of Arizona for several weeks.

UPS announced on Thursday that its venture capital arm has made a minority investment in TuSimple. The announcement also revealed that since May TuSimple autonomous trucks have been hauling UPS loads on a 115-mile route between Phoenix and Tucson.

UPS confirmed to Gizmodo this is the first time UPS has announced it has been using TuSimple autonomous trucks to deliver packages in the state.

Around the same time as the UPS and TuSimple program began, the United States Postal Service and TuSimple publicized a two-week pilot program to deliver mail between Phoenix and Dallas, a 1,000 mile trip.

TuSimple claims it can cut the average cost of shipping in a tractor-trailer by 30 percent. In an announcement about the new partnership, UPS Ventures managing partner, Todd Lewis, said the venture arm “collaborates with startups to explore new technologies and tailor them to help meet our specific needs.”

UPS would not share the terms of the deal with Gizmodo. TuSimple did not immediately respond to a request for comment.

As the Verge reports, TuSimple puts its own autonomous tech—which relies on nine cameras and two LIDAR sensors—in Navistar vehicles.

Home / News / UPS Has Been Delivering Cargo in Self-Driving Trucks for Months And No One Knew UPS Has Been Delivering Cargo in Self-Driving Trucks for Months And No One Knew 10:51 1 Comment - News The self-driving freight truck startup TuSimple has been carrying mail across the state of Arizona for several weeks. UPS announced on Thursday that its venture capital arm has made a minority investment in TuSimple. The announcement also revealed that since May TuSimple autonomous trucks have been hauling UPS loads on a 115-mile route between Phoenix and Tucson. UPS confirmed to Gizmodo this is the first time UPS has announced it has been using TuSimple autonomous trucks to deliver packages in the state. Around the same time as the UPS and TuSimple program began, the United States Postal Service and TuSimple publicized a two-week pilot program to deliver mail between Phoenix and Dallas, a 1,000 mile trip. TuSimple claims it can cut the average cost of shipping in a tractor-trailer by 30 percent. In an announcement about the new partnership, UPS Ventures managing partner, Todd Lewis, said the venture arm “collaborates with startups to explore new technologies and tailor them to help meet our specific needs.” UPS would not share the terms of the deal with Gizmodo. TuSimple did not immediately respond to a request for comment. As the Verge reports, TuSimple puts its own autonomous tech—which relies on nine cameras and two LIDAR sensors—in Navistar vehicles.

The partnership announcement states that TuSimple has been helping UPS understand how to get to Level 4 autonomous driving where a vehicle is fully autonomous and able to reach a particular location. At this point, the TuSimple trucks carrying packages for UPS still have an engineer and a safety driver riding along. When UPS reaches Level 4, it won’t need anyone behind the wheel.