。
Traffic accidents happen day after day.
Literal
Day-after-day traffic-accidents [subject-が] occur.
A compact, headline-style statement. 連日 ('day after day, every day for a stretch') is adverbial and more emphatic than 毎日 — it implies continuity of the same undesirable thing. Plain form 起きる works as a general present-tense statement about a recurring situation.