A 49 year-old motorist was arrested and taken to the police station in Lerwick after failing a breath test at the weekend.
Police were responding after reports of a car driving erratically on the Esplanade in Lerwick.
A man has been cautioned and charged for drink driving. Police say a report will be sent to the procurator fiscal.
Meanwhile, a 58 year-old has been charged with dangerous driving, following claims he drove past a cyclist so close as to cause him to almost fall off his bike.
Area commander for the Isles, Chief Inspector Paul Daley said: “We would remind all motorists to ensure the give cyclists enough space on the road when passing.”