At present, governments fund investments (such as roads) through tax. Many investments are impossible because people do not have the money.
Ground rent is different. Ground rent measures the value that an investment creates. This value then pays for the investment. This is how:
Ground rent lets us measure precisely what value would be added by any change. For example, a road (or doctor) might benefit Jane by $2, but can be paid for by adding $1 to Jane's ground rent. So Jane is $1 better off and the road pays for itself.
Notes: Borrowing to build the road will be cheap, as better information means less risk to lenders. If Jane does not want the profit she can easily move, as jobs will be plentiful and mortgages cheap. If Jane's house is by the road and loses value then ground rent goes down by that much: Jane still profits.