Part of it could rest with taking business decisions out of the hands of politicians and devolving authority to the lowest level, i.e. an appointed board with no veto authority from elected officials. If a politician is responsible for making business decisions on how to run a business like a toll road or an airport, the politics will be rampant within that process.
No, no, no. Do not EVER do this! For a perfect example of what happens with this sort of setup, look at the Mass Turnpike Authority. An absolute nightmare that had ZERO accountability to anyone and filled with people hired through a patronage system who decided to raise their own pay whenever they felt like it.