Nighttime self-driving buses commence service transporting passengers between 20 stops in Seoul's busiest districts, Dec. 4. Yonhap

A couple of self-driving buses have begun their nighttime service linking the busiest areas in Seoul, the first regular late-night bus route served by automatic driving vehicles, city officials said Tuesday.

The two nighttime buses, numbered A21, commenced service Monday night to transport passengers between 20 stops connecting the Hongdae district to the Dongdaemun district, two of Seoul's busiest areas.

They will operate exclusively on weekdays from 11:30 p.m. to 5:10 a.m. the following day, covering a nearly 10-kilometer route at an interval of 70 minutes.

The city said the service marks the first time in the world that self-driving buses are exclusively used for regular nighttime public transportation routes.

The buses, converted from Hyundai Motor's commercial vehicle model Elec City, are the same size as other regular buses.

All passengers must wear seat belts for the buses to operate, and standing passengers are not allowed.

On the first day of the service Monday, two safety guards were aboard the buses, including a "test driver" who sat in the driver's seat but didn't hold the wheel. They ran at a slower speed than regular buses, maintaining a speed between 30 and 40 kph and keeping a safe distance from vehicles in front.

Seoul plans to operate the buses for free for a while before turning to a for-charge service during the first half of next year following the stabilization of the service.

The city is also considering expanding the bus route and introducing self-driving buses to other regular long-haul routes linking city centers to suburbs, city officials said. (Yonhap)