In the UK the Mayor of London, Sadiq Khan, has announced that Transport for London is working on bringing 4G connectivity to the London Underground.
Trials will soon be taking place (initially on the Waterloo and City line) to test the technology and also try to ensure that it will be able to support 5G in the future.
Transport for London is also looking at how it can make it commercially viable. It will be looking for feedback from the public and will work with industry to see how it could make it profitable.
Deployment is planned to start in 2019.