。
I think walking alone at night is dangerous.
Literal
Night-road [obj-を] 1-[counter-人] [with-で] walk-[nom-のは] dangerous [quotative-と] am-thinking-[polite-ます].
夜道 ('night road, dark road') is a noun compound with a slightly ominous feel. １人で ('alone, by oneself') uses で to mark accompaniment/manner. 歩く takes its traversed path with を. The whole nominalized clause is the subject of 危険だ, followed by the quotative ~と思う.