What is street abandonment?

It means the public entity no longer wants to own or maintain the street, or be liable for damage or injuries occurring there. There may be overlapping rights, as where a federal highway is designated on top of a state highway which is on top of a city street which is on top of an old railroad bed which was taken by eminent domain for a "public purpose".

It is also possible to "abandon" streets that were only laid out on paper, such as new subdivision, which were never actually built. These may be privately or publicly owned streets, and is a tricky area of law.

Your local laws and regs will outline the procedure for official abandonment or implicit abandonment of previously public ways or dedicated private ways, and this raises the question of "who should now own the street?" In many places the adjacent landowners will acquire title to the portion of the roadway that is defined by their existing frontage lines and the centerline of the road.

However, there may be pre-existing deeds in which one owner or some completely different owner has retained a right of reversion for themselves and their heirs and assigns.

I happen to own one of those myself, claiming nearly a mile of land (fifty feet wide) beneath what is currently occupied by a public road "right of way", which is not maintained by the town. It the town abandons the road, it reverts to my ownership, including any private easements other neighbors may have acquired by deed.