The sample 5%/year loan payment already includes the interest and principle repayment, where the interest rate incidentally is about 3%. Annual debt service is

The sample 5%/year loan payment already includes the interest and principle repayment, where the interest rate incidentally is about 3%. Annual debt service is 5% x 60% of GDP = 3% of GDP. As the GDP grows, the portion of the debt service each year becomes less and less, 2.9%, 2.8%, ... The train system presumably generates revenue, where the operating income can be used to pay off the debt, rather than paid by tax on the GDP. A train system has transformative benefits to a nation. The benefits are still there long after the debt is gone. The ROI period is way longer than 30 years.