SHANGHAI -- A mobile app has been made available to enable passengers within the Yangtze River Delta to travel on three inter-city railway lines without a paper ticket, part of efforts to promote the integrated development of the area.

Passengers who have registered and deposit enough money in advance can get a QR code at the app of "railway e-card" and scan it before boarding trains on the Shanghai-Nanjing, Nanjing-Anqing and Nanjing-Qidong lines, according to the China Railway Shanghai Group Co Ltd.

Designated seats have been reserved for these passengers, and they need to scan the QR code again at the exit gate to have the fare deducted after getting off trains.

Passengers who want to get the fare reimbursed can have a paper invoice from a ticketing machine at train stations within 31 days.

The e-cards, which allow passengers to board any train on the lines like buses, will bring much convenience to numerous people commuting within the Yangtze River Delta, which consists of Shanghai Municipality and the provinces of Jiangsu, Zhejiang and Anhui.

Last year, China unveiled an outline for the regionally integrated development of the Yangtze River Delta, which is one of the country's most economically active, open and innovative regions, and produces about one-fourth of the nation's GDP.