My laughter is about your feasibility. You are saying it will be lighter on the pocket of the passengers right. Well people of Kerala are very much educated they will instantly know what's worth it or not. People in Kerala simply wouldn't wanna move just north to south to the state. They would like to travel to further places as well beyond the borders of the state and that's where this issue is. This is a standard gauge semi-high speed line which means it will require a separate rolling stock and so no IR traffic can enter through it plus there would be no unified high speed railway system if multiple different systems are established. Let's say Kerala makes this and the whole North is covered into Bullet Train network then they wouldn't be able to connect together. Another thing is Kerala is one of the most beautiful places in India....
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Destroying those forests covering Kerala would impact on environment a lot compared to what the current bullet train is doing which is not even passing through any major forest. Kerala government should rather spend this money on upgrading existing IR lines and making them 160kmph compatible then making a whole new defunct line which would not be able to go further beyond the borders of Kerala.