Plate numbers of drivers who honk over legal limit are live-streamed on an electronic screen in Hangzhou, Zhejiang province. [Photo/zjol.com.cn]

A digital system which can automatically detect and identify vehicles whose horns are over the legal decibel limit has approved effective since it was put into use in Hangzhou in July, local media reported.

Nicknamed "sonar police", the system has helped police officers in Hangzhou record and punish more than 7,300 cases of illegal honking. Plate numbers of the violators are livestreamed on electronic screens that have been placed at busy and significant places in the city.

The number of illegal honking cases at busy crossings, for example at the Ding'an intersection of West Xihu Ave, has plunged from more than 100 a day to the present 30 at most.

Movable "sonar police" devices were also available at some crossings. Consisting of a camera panel and a lifting support, the system can adjust the camera to higher or lower positions due to traffic conditions.

"Generally, the camera can detect and identify vehicles that are in front of it and at a distance of 30 to 40 meters," said a police officer.

The system is an example of Hangzhou's dedication to making the city more intelligent with various digital governance measures. It also reflects Hangzhou's determination to prevent noise pollution and bring quiet back to people.

A movable "sonar police" can detect and identify vehicles that are in front of it and at a distance of 30 to 40 meters. [Photo/zjol.com.cn]