A pedestrian was struck and killed by a vehicle Saturday on the northbound New Jersey Turnpike in Mercer County, leading to major traffic backups in the area, authorities said. State Police are investigating why the person was on the outer roadway near mile marker 68.4 in East Windsor when the crash took place about 12:25 p.m. Two right lanes remain closed just after 3 p.m. north of Exit 8, with traffic slow through the area, according to 511nj.org, the state Department of Transportation’s traffic website. The identity of the pedestrian will be released pending family notification. The driver …