Prices are set dynamically based on usage, and there is competition from the free lanes that run parallel and serve the same locations.

The 495 HOT Lanes were built through a public/private partnership. The private consortium, who paid for the expansion, received toll collecting rights from Virginia for the next 80 years. A for-profit has absolute control over this regressive tax...

"The companies, which will finance all but $409 million of the project, have an 80-year agreement that will allow the partners to collect tolls from motorists who use the lanes." [1]

[1] http://www.washingtonpost.com/wp-dyn/content/article/2007/12...

Ok, so a company has been delegated the authority to levy tolls. But the authority comes from the government.

They built those roads specifically to be express lanes, and fund them via these tolls. Similar to the Triboro Bridge in New York, built to help commuters get to Manhattan faster/MUCH easier and infeasible to build without charging tolls.

The principle of supply and demand can exist outside of the context of a free market. As long as there's some mechanism to set the price based on a balance of the two variables.

But public roads are usually for the use of the public. At most there's a difference of a few dollars if you're just traveling a short distance. This arrangement just seems to be milking people for money, and I don't want to see public spaces go in this direction.

These toll lanes were built and are managed by an Australian company, Transurban. In the linked article it mentions that sensors in the toll lanes adjust prices relative to demand.

???

There's plenty of private roads and bridges.