Bridges are not public goods. Public goods are non-excludable and non-rivalrous. Bridges are both excludable (people can be prevented from crossing unless they pay a toll) and rivalrous (only so many people can use a bridge at once). This makes them a private good. Yes bridges are funded by governments with revenues collected from taxes, but that doesn't change their economic classification.
And the main cost of bridges is not materials, it's design, permitting, and construction. For example: Adjusted for inflation, the new San Francisco Bay Bridge span cost $8.6 billion. Its 450,000 cubic yards of concrete weigh around 1.3 million tons, for a cost of around $6,000 per ton. Concrete is $50-75 per ton, so that's 1% of the cost.
That was a very narrow definition of a public good.
Not preventable? (Excludable)
Not limited in supply? (Rivalous)
What can even be defined as a public good. Can air even be a public good by this definition? Even arguing in good faith I cannot wrap my head around this.
A hospital? Limited capacity even with socialized medicine. Not a public good?
Is this just an (to me) alien and extreme libertarian viewpoint I cannot fathom or am I missing something deeper?
The concrete example stands. But a world in which we do not consider bridges a public good seems rather dystopian to me. I grant you that some of those might be private. But considering all to be private and just with a handwave acknowledge that most are publicly funded seems... Odd...
I am using the Econ 101 definition.[1] Examples of public goods include lighthouses, knowledge, a common language, and national defense.
The reason for the different classification is because public goods obey different economic laws. For example: because public goods are non-excludable, they have the free rider problem.
And the main cost of bridges is not materials, it's design, permitting, and construction. For example: Adjusted for inflation, the new San Francisco Bay Bridge span cost $8.6 billion. Its 450,000 cubic yards of concrete weigh around 1.3 million tons, for a cost of around $6,000 per ton. Concrete is $50-75 per ton, so that's 1% of the cost.