I think where I get stuck is that there is no competition with roads, in a densely populated area. So it would be run by one company. Right? It's ripe for monopolies. It isn't like there would be parallel roads charging tolls by different companies.
Discussion
That there's no competition for such roads is the status quo, and with gangsterment building them you are forced to pay for them, whether you use them or not, and even if you don't pay direct taxes.
They force everyone except gangsterment members to pay for such projects through currency inflation tax, while such members get the vote buying benefit and a cut from your money.
Neither is it certain that such roads would not have competition. Look at history of railroads and city trolley companies.