 Many traffic accidents, some fatal, have caused traffic jams and closures since I-84 was opened.One was notable for the type of vehicle involved; another led to a still-open murder investigation.On August 6, 1976, drivers along I-84 near exit 18 (NY 311) in the Putnam County town of Patterson saw a low-flying helicopter cross over the interstate and then get entangled in the power lines passing overhead.