To add to the other comment about public-private competition (another example is schools - parents in private schools pay for both), the mostly-private industry managed to build inter-city railroads and local streetcars just fine. It is not obvious that it wouldn't eventually build highways if there was vision and/or existing demand.

Who knows, it might have even achieved a reasonable balance between the two, instead of forcing a car-centric environment everywhere like the public option? ;)