What is an example of the free rider problem in economics and how does it impact the allocation of resources?

An example of the free rider problem in economics is when people benefit from a public good without paying for it, such as enjoying clean air in a park without contributing to its maintenance. This can lead to underinvestment in public goods as individuals have little incentive to pay for something they can enjoy for free, resulting in a misallocation of resources and potentially lower overall welfare for society.