The Hearth Tax (1662-89) is the only national listing of people between the medieval poll taxes and the 19th century census returns. It was a property tax, assumed to approximate to the householders' wealth, measured by the number of their fireplaces.
But there is no suggestion that it was "ringfenced' for the upkeep of roads.
I wish you would come clean and show that all your questions are from Quizmail December. People generally only give hints to Quizmail questions not complete answers but you've very neatly got round that.