The Léman Express is proving so popular, the system is struggling to keep up.
There aren’t enough trains and passenger space is being squeezed. New double decker carriages are not expected to be ready until 2030.
The company running the service, Lémanis, says it's not just cross border workers and commuters using the trains, off-peak services are also busy and only a quarter of the traffic is from France.
It’s also finding some platforms are too short and the single-track line in some areas in France is causing problems.
To fix those issues will require public funding.