The phrase 'railway extension' is correct and usable in written English.
You can use it when you are referring to a railway line that has been built to extend an existing rail network, or when discussing plans to extend a rail network. For example: "The government has recently approved plans for a railway extension to connect London and Manchester."
Reviving plans for a Docklands Light Railway extension to Dagenham Dock would be good.
Plans are well advanced to build new Thames river crossings, a Docklands Light railway extension and a tram system together with road improvements to the A13 arterial road.
Workers began construction Sunday on a railway extension to connect the Tibetan capital, Lhasa, with the region's second-largest city, Xigaze, state media reported.
A railway extension is under way to Hambantota; in the far south of the country, it is the Rajapaksa power base.
China is extending huge loans to Sri Lanka for post-war infrastructure development, with Chinese workers doing much of the construction on seaports, a new airport, highway and railway extension projects and power stations.
By the late 1890s a harbour crossing and a city railway extension were again on the agenda.
Both surface and underground railway extensions were completed to the eastern suburbs in 1979.
"Instead a package of non-road alternatives such as DLR (Docklands Light Railway) extensions, ferries and cheaper bridges for walkers and cyclists must be considered".
Initially, Hayes tried to promote railway extensions to his hometown, Fremont.
The bill received Royal Assent on 9 August 1899 as the Brompton & Piccadilly Circus Railway (Extensions) Act, 1899.
After the war, railway extensions took the UERL's services out into suburban areas to stimulate additional passenger numbers, so that, by the early 1930s, the company's lines stretched beyond the County of London and served destinations in Middlesex, Essex, Hertfordshire and Surrey.
