A fully-automated rail system using carriages made by a Japanese company has begun operations in Honolulu in the US state of Hawaii.

The initial segment of the Skyline system opened Friday. It runs about 17 kilometers, connecting nine stations from the vicinity of central Honolulu to the city's outskirts in about 20 minutes.

Rainbows, often seen in Hawaii, adorn the train cars manufactured by Hitachi. The cars also provide space inside for bicycles and surfboards.

This is the first autonomous rail system in the US. Trains are controlled from an operations center located in the outskirts of Honolulu.

At the opening ceremony, Honolulu Mayor Rick Blangiardi expressed his gratitude to all the attendees, saying the rail system is historic and transformative.

After the ceremony, local people boarded the trains and enjoyed a ride.

The rail system is expected to reduce vehicle use and ease congestion on expressways, as well as reduce emissions of carbon dioxide and other greenhouse gases.

The operating segment will be extended in steps to Hawaii's international airport as well as central Honolulu. The operator hopes to open the entire line by 2031.