Nowadays, the BigBang of metropolitan railway systems in mainland china is remarkable, but I have a question about it.

Today, the expansion of each city's subway networks leads to the connection between two different lines at final stops(like 花橋 sta. of Shanghai 11 line and Suzhou 11).

However, this style still requires passengers to get off a train and transfer to another. This is inconvenient, therefore I recommend introducing "through-service" between two services.

An outstanding example of this is Japan; Metropolitan railway systems in big cities like Tokyo and Osaka are fragmented into "territories" of multiple train operators(JR, municipal subway, privately-owned rail companies), but they try to unify their system standards and combine their tracks into one long service.

Another one is RER in Paris, which imitates Japan's action and coupling lines operated by the RATP(Paris municipal operator) and the SNCF(France National Rail). This enables passengers to traverse Paris central, traveling from one of its surrounding suburbs to another.

With all the differences of train construction systems(like signals and operating methods), china can do this too.

What's your opinion?