Four Montgomery County residents, including a U.S. Naval Academy midshipman, died in separate traffic accidents in a 24-hour period between Friday and early yesterday morning, police said yesterday.

The midshipman, Timothy Powell Scott, 18, of Falls Road in Potomac, was killed Friday morning when his car ran off Route 26 in Sykesville in Carroll County, struck a telephone pole and crashed into the front porch of a house. Maryland state police attributed the accident to speeding and driving while intoxicated.

Two midshipmen who were passengers in Scott's car were injured, one seriously. Richard Michael McBride, 19, of Houston, Tex., was in serious condition yesterday at Baltimore County Hospital. Bret Muilenberg, 19, of Titusville, Fla., was treated at Baltimore County Hospital and released.

On Friday night, Anthony Anselmo, 90, of 4410 Randolph Road, Rockville, was struck by a car as he crossed the intersection of Randolph Road and Selfridge Road. Anselmo was taken to Suburban Hospital, where he died about three hours later. The driver of the car, a 19-year-old girl, was not charged, police said.

Shortly after the Randolph Road accident, a 21-year-old Bethesda woman who was a passenger on a motorcycle was fatally injured when the motorcycle went out of control and struck the median strip along Old Georgetown Road in Bethesda. Both the passenger, Irene Dykermay, and the rider, Howard Van Winkle, 22, of Rockville, were taken to Suburban Hospital. Dykermay died early yesterday morning. Van Winkle was treated and released. Police are investigating the cause of the accident.

Early yesterday, a 19-year-old Derwood boy was killed when his car struck a telephone pole and a tree. County police said Kenneth William Hanks of 7812 Potters Mill Court was driving his car northbound on Laytonsville Road in Gaithersburg when it went out of control and crashed. Hanks was dead at the scene, police said.