The gate is so narrow that the car can't get through.
Literal
Gate [topic-は] very narrow-[and-て] that car [subj-は] cannot-pass-[potential-れ][polite-ません].
Te-form of adjective 狭くて ('being narrow, and so') chains into the consequence 通れません ('cannot pass'). The te-form with adjectives can express causal relations too, similar to verbs.