Hyundai Motor has successfully tested a semi-autonomous large trailer truck on a domestic expressway.

The company said Wednesday that it tested the level three autonomous driving technology the previous day on a 40-ton truck and trailer on a 40-kilometer section of highway connecting the cities of Incheon and Uiwang in Gyeonggi Province.

The truck, equipped with level three autonomous driving technology as defined by the U.S.-based Society of Automotive Engineers, was the first large-sized truck to obtain a temporary self-driving permit from the Transport Ministry in late June.

Level three, out of a total of five levels, is an intermediate stage in the self-driving technology, allowing lane changes and other driving functions to work without intervention by a human driver. 

A level three vehicle can automatically travel a predetermined path while avoiding obstacles, but a driver must intervene in dangerous situations and other emergencies.