Governments should carry out comprehensive tests on a self-driving car's claimed capabilities. This is the same as cars without proven passenger safety (Euro NCAP) aren't allowed to be on roads carrying passengers.
Any Legislative body can do so. There's no reason to limit this strictly to the federal government. States and municipalities should have a say in this as well. The _citizens_ are the only entity that _decide_ if beta technology can be used or not.
> comprehensive tests on a self-driving car's claimed capabilities.
This presupposes the government is naturally capable of performing an adequate job at this task or that the automakers won't sue the government to interfere with the testing regime and efficacy of it's standards.
> aren't allowed to be on roads carrying passengers.
According to Wikipedia Euro NCAP is a _voluntary_ organization and describes the situation thusly "legislation sets a minimum compulsory standard whilst Euro NCAP is concerned with best possible current practice." Which effectively highlights the above problems perfectly.