You could certainly build freeways/bridges as toll roads. All the 19C railways were built like this as are modern mega projects like the channel tunnel. There

You could certainly build freeways/bridges as toll roads. All the 19C railways were built like this as are modern mega projects like the channel tunnel. There are some problems - do you allow compulsory purchase of land? If not then a single person can ransom your project if you do then you need government approval for each project. Upto 25% of the cost of some 19C railways were in legal fees to get the legal acts needed to build them