近隣 and 隣接: the vicinity and adjoining places
Compare houses and residents in the vicinity with a park adjoining a library, without turning adjacency into a guarantee of transport.
An area and residents in the vicinity
近隣（きんりん） means the neighboring area or vicinity. 「火事を知らせるため近隣の家を一軒ずつ回った。」 describes going from house to house in the vicinity to warn people about a fire. 知らせるため gives the purpose, not a result that every resident was notified.
「近隣住民への説明会が公民館で開かれた。」 says that an information session for nearby residents was held at the community center. 近隣 modifies the residents' local area; their attendance count is not stated.
Places adjoining each other
隣接（りんせつ） means adjacency. 「図書館に隣接する公園で昼食を取った。」 describes eating lunch in the park adjoining the library. The park and library are read as neighboring places.
「二つの町は隣接しているが、交通手段が少ない。」 says that the two villages are adjacent but there are few means of transportation. Their adjacency does not establish plentiful transport or guaranteed direct connections.
A nearby range and a neighboring arrangement
The 近隣 houses and residents are selected from a nearby range. The 隣接 park and villages are placed in a directly neighboring relationship. The examples provide no fixed distance or number of houses defining 近隣.
Adjacency is not defined as a situation requiring hand contact. The modifier identifies whether the sentence refers to a nearby area or to a place adjoining another place.
Does 二つの町は隣接しているが、交通手段が少ない。 mean that transportation between the adjacent villages is plentiful?
Show the answer and why
No. It states both adjacency and a scarcity of means of transportation. 隣接 alone does not guarantee the degree of transport connectivity.