The preferred route for Auckland's proposed billion-dollar central city underground railway system has been released.
The track will run in a loop from Mt Eden to Britomart station with three stations underneath Khyber Pass Road, Karangahape Road and Albert Street.
Auckland Regional Transport Authority chairman Rabin Rabindran told Morning Report they are preparing a business case to try to advance the project.
If approved, the underground trains will be in operation by 2020 and could then be extended to other areas.
Mr Rabindran says Auckland's population is going to grow substantially in the next 40 years and the underground loop system would be much more effective than the current dead-end line.