A 9-year-old runaway driving a van on Interstate 95 fled police at speeds up to 100 mph before crashing into a guardrail while his teen-age companions slept in the back, state police said. The boy was in critical condition at Johns Hopkins Hospital today with head and chest injuries, while his 14-year-old brother and their 12-year-old friend were in satisfactory condition, police said. The boys' names were not released because of their ages, and investigators were to meet with the youngsters' parents this morning, Maryland State Police Sgt. James Black said today. The three boys, from suburban Trenton, N.J., apparently were en route to Florida on Thursday in the van owned by the 12-year-old's parents, police said. The older boys were asleep in the back of the van during the chase, Black said, and are not cooperating with investigators. State police said they were told that a van was being driven erratically on the Delaware Turnpike, just across the Maryland line. The chase began when a Maryland trooper signaled the van to stop and it accelerated to speeds of up to 100 mph. The driver lost control, and the van veered across the median strip, slamming into a guardrail and overturning on the northbound lanes about 10 miles north of downtown Baltimore, police said.