I pay taxes that go to pay for the roadways and highways near you. You don't pay the actual costs of building and maintaining those roads as the tax burdens get spread all around. Some of my taxes have also gone to overthrow dictators, prop up existing dictators (like Saudi Arabia) or to put dictators into power (such as the Shah) so that we could have cheap oil. Politicians have repeatedly claimed that oil revenues from Iraq would pay for the war and reconstruction of Iraq.

The roads are certainly built and maintained with capital diverted from more productive uses. Even if the postal service didn't lose money hand over fist I'd still call it subsidized, as it wouldn't exist without its legal monopoly.

One can argue whether road costs are covered by user fees or not. The subsidized policing and EMS costs are typically ignored, for example. You might want to include some of the military and intel budgets related to oil security.