"We're only needed when the high-speed train is delayed, and our only regular riders are those staff taking late shifts and working at the airport," he said.

Tan remembers the faces of almost all his regular passengers, as well as where they usually get on and off as "there are only several of them".

It takes 65 minutes to make the 30-km trip to the Bund, with more than 40 stops on the way, said Tan.

"I wouldn't expect any single rider for the first two rides, you will get a few on the third one, and after 1 am the only passengers on the bus would be those airport staff - and there aren't many."

Wang Hongzhen, Tan's wife who quit her job years ago, said lunch is the only meal of the day that she could eat with her husband.

"Dinner for my daughter and I is about 6 pm, but my husband wouldn't wake up until 9 pm. I usually save him some food and prepare him lots of snacks for the long night shift," she said.

In his attempt to answer why there are fewer passengers nowadays, Tan said many of Shanghai's local factories and companies had a three-shift schedule during the 1980s and 1990s and midnight buses used to be their shuttle bus.

"But that's no longer the case with more and more companies getting rid of three shifts and having their own shuttle buses," he said.

"It's not popular for teenagers to take the bus either when they go out at night - they'll just take a cab if it's too late."

As for No 4 Bus Company, which puts five buses and seven drivers on Route 316 so that the wait for the next bus is limited to 30 minutes, it is not at all cost effective.

With about 125 daily riders on the route, the company is not even close to covering its costs of more than 1,100 yuan per night per bus.

"What we earn covers only one-tenth of the total costs - it is so little that it could be considered negligible," said Yu Zude from No 4 Bus Company's department of operations. "The company's biggest wish is to reduce the five buses (dedicated to Route 316) to four, and then from four to three and to two." But as a public service of the city, the bus is required to be on the road.