A subway line that links downtown Beijing with Da­xing International Airport in the Chinese capital now allows passengers to enter and exit stations by just scanning the palm of a hand, setting an example of how using biometric data in public transportation can make commuting more convenient.

The pilot program was launched on Sunday on the Da­xing Airport Express subway line to spare passengers the trouble of swiping a card or scanning a QR code to catch a train, the Beijing Municipal Commission of Transport said.

Any commuter age 14 and above can first register the print of either palm through a simple, automated process and provide relevant information to authorize the payment gateway of WeChat, a popular messaging app in China.

Once the palm print is registered, a commuter can scan the palm at any automated ticket gate to pass through. The fare is automatically deducted after exit.

"Passengers can just place a palm above the scanning machine when entering or exiting a subway station. The ticket gate will open if the palm scan matches the palm print registered voluntarily," said Zhang Li, an expert at the Beijing Metro Network Control Center.

The ticket gates can recognize the user's palm print and veins without contact, which is more hygienic, faster and safer than conventional check-in methods, Zhang said.

The biometric method combines the use of palm print and vein mapping, which are different for every individual. The registration is a one-time process and doesn't require renewal. The commission said data masking and encryption technologies have been applied to protect user information.

Xin Jianhua, general manager of the public service center at WeChat Pay, said palm scans can be gradually used in offices, schools, gyms and restaurants, as it requires no contact and is therefore more safe and efficient.

"Currently, it is very useful for the elderly and those who have physical limitations. They can take the subway without using smartphone apps," he said.

Use of biometric data allows passengers to take subway trains if they do not have cash or when they forget their subway cards, he added.