Four days after a giant rainstorm inundated Beijing, Liu Gang says his successful attempt to rescue people stranded on one of the city's expressways remains fresh in his memory.

On Saturday, the 25-year-old man saved more than 170 people who had been trapped by floodwaters on a section of the Beijing-Hong Kong-Macao Expressway.

"I got out of my car really quickly after I saw it was waterlogged and that the rain wasn't going to be stopping for a long time," said Liu, who works in Beijing's Changyang township, managing the affairs of people who lack residence permits. "I ran up to a patch of higher ground that happened to be next to that particular section, which is about 500 meters below the expressway's Nangangwa Bridge."

Before escaping from his car at about 7 pm, Liu had been driving to Beijing's central business district from his home in the city's Fangshan district.

Hundreds of rescuers carry sandbags to build a 2-km long floodwall at a section of the Beijing-Hong Kong-Macao Expressway in Beijing's Fengtai district on Wednesday. Liu Ping / for China Daily

"The section was in a depression and was jammed with traffic," he said. "Many of the cars there were waterlogged and many of the people were helpless. I didn't think twice. What I really wanted to do was to save more of them. So I shouted at some of the people I saw and asked them to climb onto their cars' roofs as quickly as possible.

"In the meantime, another five drivers escaped from their vehicles and they helped me find some things around that place that we could use in the rescue."

Fortunately for him, members of a construction team were working about 400 meters away from the bridge. Liu asked some of them to help.

"I told them how dangerous the section was and said it was a matter of life and death," he said. "Suddenly, about 200 of them agreed to join me and showed that they really were willing to help these stranded people."

As the rescuers ran to the inundated section of the expressway at 9 pm, carrying eight life buoys, two ropes and several flashlights, the downpour continued, unleashing swift currents.

By then, the water flooding the expressway section had risen up to the thighs of people who were standing on the roofs of vehicles, among which were three buses, Liu said.

"I tied one end of a rope to a tree that was up in a higher place and, with the other end and some life buoys, swam to the stranded vehicles."

The rescue did not go as smoothly as Liu had expected. Some of the trapped people snatched at his rope without awaiting their turns and refused to heed his instructions.

Liu told them he was a police officer, and said that older people, women and children should be the first to leave the dangerous section.

"I had to pretend I was a policeman," he said. "That was the only way to get these people, who were panicking, to pay attention and calm down."

Liu had once served in the army, an experience he found to be of great value on Saturday.

"I learned about rescuing people when I was a soldier," he said. "And I knew the most important thing for me to do was to first try to help the people who were weakest."

One of the men Liu rescued was in his 20s and had just undergone surgery in Beijing. When the disaster struck, he was on a bus with his grandmother, both on their way back to their home in Shanxi province.

"She at first wouldn't let me rescue the young guy and insisted on staying with her grandson," he said.

"I pushed a life buoy down onto the poor guy's body and asked a worker to help get him up to higher ground. I also tried to comfort the old woman by telling her everything would be all right."

Liu also rescued a pregnant woman and an elderly man who had suffered a cerebral thrombosis.

"Actually, I had no time to think about how dangerous these rescues were," Liu said. "All I knew was that I wanted to save more people."

He said he also made it a point to comfort people who were frightened and to try to maintain order.

When people stranded in the expressway section started trying to move to higher ground, workers were often there to guide them with the use of flashlights. Others escorted the recently rescued to a small yard used by the construction team.

"The workers even carried weak people to safety on their backs and gave us rooms to rest in," Liu said.

The work ended at about 2 am on Sunday when military and police crews from the city's center arrived at the expressway with food and drinks.

During the rescue, Liu's father tried to call him many times but couldn't get through until Sunday morning.

"I knew my family was worried about me," Liu said. "I left my phone in the yard so it wouldn't interfere in the rescue work."

Zhao Shan, 26, one of Liu's colleagues, was not surprised to learn that Liu had saved people on the expressway.

He said Liu's willingness to help others has a lot to do with his character and with the place he works.

"Liu is an outgoing and brave man who shoulders responsibility," Zhao said.

"He likes helping others. His work has him talking with all different sorts of people. That has helped to make him really good at communicating."

Yu Yaping, director of the municipal flood prevention authority's information office, praised Liu's rescue work and said now is a good time to teach people how to rescue themselves in disasters.

"After all, professionals need time to conduct rescues," he said.

"So it's essential to learn how to save their time by knowing how to rescue yourself."