An ambulance in Hangzhou, an eastern Chinese city, avoids gridlock and all red lights switch to green as it approaches.

"The travel time was cut to half," said Sun Shixiang, of Hangzhou's public security bureau, while pointing to a big screen.

The progress is attributed to Alibaba's "City Brain", an AI platform on Alibaba's cloud infrastructure. It is a support to cities in digital transformation.

Around half of the world's population lives in urban areas. Traffic congestion goes along with urbanization.

In Hangzhou, the "City Brain" pulls in traffic and weather data and analyzes real-time traffic flow, adjusting traffic lights accordingly.

Over the past year, the technology has controlled traffic lights in 128 intersections in Hangzhou. The average speed of cars on these roads has increased by 15.3 percent, and travel time on bridges similarly reduced.

In addition to transport, the technology is expected to provide solutions for the city's energy and water supplies.

"City Brain" is active in cities such as Hangzhou, Suzhou and Quzhou. Outside China, Kuala Lumpur in Malaysia will soon adopt the system.

"Artificial intelligence will become important for all cities, helping them achieve sustainable development," said Wang Jian, Alibaba's technical committee chair.