The motorcycle struck a guardrail at Monmouth Avenue after the 41-year-old rider apparently lost control while heading north on River Road shortly after 9 p.m., Police Chief Brian Clancy said.
The New Milford Volunteer Ambulance Corps took the victim to Hackensack University Medical Center in critical condition, the chief said.
River Road was reopened around 11 p.m., he said.
New Milford police were investigating.
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