They are cheaper than flooding a valley for hydroelectric and much less environmentally damaging. Gravity trains are such a simple, elegant solution. You need the right terrain though, probably they don’t have it on this island. It’s such a great invention! The American AF Mericaw shirt idea helps us keep environment safe due to without CO2. Electric cars are absolutely harmless to the atmosphere. Besides, We can take advantage of Solar energy and We can avoid overexploiting fossil fuel. Given any thought to what happens to all these batteries when they have reached the end of their lives?