Hangzhou Metro has launched a new service on lines 5 and 6, which informs passengers of the congestion level on the upcoming train using a color coding scheme, local media reported on July 22.

The colors will be displayed on screens on platforms and inside cars. They will represent the congestion level of each car.

"Green means that there are less than 160 passengers on the subway car, while yellow means that the number of passengers is between 160 and 240. When the number exceeds 240, the color will turn red," said Li Na, a spokesperson of Hangzhou MTR Co. These data are collected by calculating and analyzing the weight of cars and will be displayed immediately.

In addition to Hangzhou, Beijing, Shanghai, and Guangzhou are also striving to upgrade their metro services.

The Beijing Metro completed similar upgrades at the beginning of this year. There are four colors: red, brown, yellow and green. Red means that the car capacity has exceeded 50 percent, brown is 40 to 50 percent, yellow is 30 to 40 percent, and green is below 30 percent.

Passengers are able to check the congestion level and temperature of subway cars on their mobile phones. The service will soon cover all lines of the Shanghai Metro.