The 57-year-old Watertown woman was riding an electric bicycle along Gerry's Landing Road around 6 p.m. when they crashed with a 2019 Volkswagen Golf Alltrack, State Police said.
Paramedics rushed the woman to Beth Israel Hospital with serious injuries. The Volkswagon driver, a 75-year-old Somerville man, was not hurt.
Police have not released the either of their names.
Cambridge police are working with State Police crash experts to investigate the incident.
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