The plans were announced recently by the state's first minister Mr Oommen Chandy.
The first $US 8bn phase will connect the state capital Trivandrum with Kochi and should be completed by March 2018. The second phase will run north from Kochi and is expected to be completed by March 2020.
The project will be developed jointly by Kerala state and the Indian government under the guidance of Mr E Sreedharan, who recently stepped down as managing director of Delhi Metro Rail Corporation. "Japanese technology would be introduced," Sreedharan says. "The feasibility report has already been prepared."
About 80% of the cost will be funded through debt. Kerala is trying to obtain a soft loan from the Japanese International Cooperation Agency, and plans to raise $US 20bn from a multilateral financial institution.
Kerala will also promote the project at the Emerging Kerala global investor meeting to be held in Kochi on September 12-14.