The operator of Beijing Subway says more than 4 million people have downloaded its smartphone app since a new payment system was installed at metro stations across the Chinese capital on April 29.

“Up to 20,000 users are joining the system each day to pay for rides using the app, rather than using transit cards,” said Zhou Yang at the capital’s subway management information center.

Using the app, passengers can now scan a QR code at station turnstiles to access platforms.

Not only is the new payment method fast, but it also prevents cards from being lost or stolen, according to the center.

Beijing has 22 subway lines and 370 stations, including 56 transfer stations.

In 2017, passengers traveled on the Beijing Subway an average of 10.35 million times a day, up 3.53 percent year-on-year.