Boston has a great public underground train system. London does too. Chicago has its wonderful “L” train network (with a horrible website). San Francisco has the BART.
Denver has two light rail lines. They would love to expand to a third line. The current economy will not allow such expansion. Solution? Go back 50 years. At that point in time, they could have done it. But then Denver was a sleepy western town with no thought of miles of tract homes.
Takeaway? Plan for the future. (Note to self.)