In the dark, early hours of Friday, as temperatures in Seoul dipped below freezing, a few passengers stood bundled in padded jackets, hands buried in their pockets. They were waiting for bus No. A160, the latest autonomous addition to Seoul's mass transportation system.

Operating exclusively in the early morning hours, the bus leaves Dobongsan Station Metropolitan Transfer Center in northern Seoul at 3:30 a.m. to head for Yeongdeungpo Station. Still in the pilot phase, it makes the 50-kilometer round trip only once a day. However, the city aims to introduce more routes for self-driving buses in response to strong demand from early commuters.

"I've been waiting to try the A160 since I heard about its launch," said 25-year-old Kim Min-soo, adjusting his seatbelt. A large monitor on the bus displayed the vehicle’s steering wheel in real-time, and Kim said he was fascinated to see it turning automatically without being touched. However, he noted that while human drivers can smoothly navigate around obstacles or gradually slow down, the autonomous bus tends to stop abruptly.

A series of announcements reminded passengers to fasten their seat belts, a safety protocol designed to prepare for sudden stops when the bus encounters obstacles.

Sitting in the driver's seat, a man introduced himself as the bus safety officer -- not a driver -- explaining that his job is to manually operate the bus when necessary, which is less than 10 percent of the route.

Also on board was a service manager ensuring that passengers complied with safety measures, noting the sudden stops that could make the ride feel slightly jarring. The A160 bus can carry 22 seated passengers; for safety, standing is not allowed.

As the bus entered the residential areas of Dobong-gu, it took on more passengers at each stop, including a number of city sanitation workers. They said they appreciated the opportunity to sit during their commute. One cleaner in her 70s, surnamed Park, noted the advantage of the earlier departure and greater availability of seating compared to the usually overcrowded No. 160 bus.

However, since the A160 operates within strict speed regulations, it is much slower than conventional buses. While waiting for the A160, this reporter was approached by a driver of the N16 route. Hearing mention of the A160, the driver remarked, "No matter how early it might leave, the A160 moves quite slowly. The regular No. 160 leaves about half an hour later, but quickly catches up and passes it. You'd get where you're going a lot faster on the regular bus."

The autonomous bus is free of charge for now, but a fare of 1,200 won ($0.90) will be introduced in the second half of next year -- a discounted rate for early commuters -- with plans for more routes in the works.

"This autonomous bus service at dawn is a policy initiated by Mayor Oh Se-hoon. It embodies Oh's philosophy that advanced technology should primarily benefit the marginalized, making it a tailored innovation in public welfare-oriented transportation," a Seoul city official said.