See which subway is busy. Then what?

The Beijing subway system has come up with a way to help passengers beat the crush by showing them in real time how crowded subway lines are.

Passenger information for the city's 19 subway lines can now be found on the system's website, and the function will be added to its official app in the near future to allow subway users easy access to passenger load information using smartphones.

Subway lines are marked in four colors - black, red, yellow or green - depending on the number of people on board. Black indicates a line that is very crowded; red and yellow means less so; and green indicates the fewest passengers.

Stations temporarily restricting access because passenger numbers exceed limits will be marked with a red and white fence icon.

The information will be updated every five minutes, a Beijing News report said. A team from the subway operator is currently testing the reporting system.

"Beijing has 19 subway lines and more than 300 stations, so the information is going to help passengers avoid the busiest lines by using a different subway route or by using ground transportation," a subway staff member told Beijing News.

But commuters are not so sure.

Zhu Zhibin, 24, who commutes to work on Line 2 and Line 5, said he doubted the new function would be practical. Beijing residents already know what lines are crowded, and when, he said.

"I have to squeeze into the train even if the app tells me it's crowded, because the subway is the only convenient way to get to work. But for people with a choice of other means of transportation, the app could help," Zhu said.

Cheng Lingfeng, who also takes the subway to work, had similar concerns, saying the function is redundant for Beijing residents but might be helpful for people with flexible travel plans.

"The information will be helpful for tourists in Beijing because they can adjust their itineraries according to traffic conditions," Cheng said.

Ma Jiu, from Shaanxi province, who travels regularly in Beijing, hints that the information, which is most useful at peak hours, is of limited use for tourists, because tourists usually avoid peak hours anyway.

"Tourists in Beijing usually do not get up as early as commuters. Aside from the peak hours, I think the Beijing subway is generally bearable and there's no need to check which is less busy. But still it is better than nothing," Ma said.

Wang Lei, who drives to work, compared the subway passenger data with real-time road information on mobile apps like Amap and Baidu Map, which also marks roads with different colors. Usually red and darker colors symbolize traffic congestion.

"Drivers can choose a less busy road with the assistance of road information, but some subway riders have very limited choices because choosing a different line or ground transportation for them means an increase in commuting time," Wang said.

Li Lei contributed to this story.