The biggest externality cost in the United States by far is parking. Many cities have mandatory parking space requirements for businesses that impact not just n

The biggest externality cost in the United States by far is parking. Many cities have mandatory parking space requirements for businesses that impact not just new developments but re-purposing of existing properties (ex: restaurants must provide so-and-so many free parking spaces per thousand square feet; you have to do this even if you're converting an existing property into a restaurant). This is a huge pain for a lot of people trying to open small businesses. This is more of a zoning issue though (I think mandatory parking ordinances should be repealed and all parking should be privatized).