"When I walked by that spot, I noticed a crack emerging on the surface and then I took a further look. I found that the color of the road surface had become abnormally darker and grey compared to elsewhere, which should be black under normal circumstances."

Minor cracks on the road might have been ignored by most people, but Li immediately recognized the signs of potential danger and decided to raise the alarm.

He reported the situation via walkie-talkie to Ye Jianjiang, his work team leader.

杭州协警礼为奇

"When he reported the case to me, I gave him instructions through my walkie-talkie, ordering him to segregate the vehicle flow and prevent the cars from entering that problematic area, since the heavy weight of a vehicle could easily cause serious collapse on the road."

Ye said he could also see something was very wrong with the cracked road surface.

"When I took a closer look into the crack, I saw some pebbles inside sliding to the bottom, just like a large amount of stones and sand sliding down from a hopper of a truck. The area of the hollow had also enlarged greatly."

The police then began to stop the traffic and direct all the passing cars to make a detour and not to pass over the road surface, which they then cordoned off with traffic cones.

Just 4 minutes after Li first noticed the crack, and took measures to control the traffic, the hole suddenly widened into a 20-square-meter-wide, 2-meter deep sinkhole big enough to swallow a couple of vehicles.

Thanks to Li's timely response and actions, nobody was injured.

The initial anger of drivers at being stopped by Li, turned to gratitude towards the police officer for saving their lives.

The surveillance video was later uploaded by cnn on its official Facebook account, which received over 3.6 million clicks and about 20 thousand re-posts.

Many people on social media praised Li's heroic and fast actions, hailing him as a hero traffic policeman.

The city government of Hangzhou has also nominated the officer for a first-class public security award.

The cause of the road collapse turned out to be the construction of the city's metro line 2. Emergency repairs have been made and traffic in the area is now reportedly back to normal.

For CRI, I'm Xie Cheng.