Howard County police are investigating a fatal single-vehicle collision that took place in Columbia on Friday afternoon. At approximately 12:53 p.m., a 2015 Toyota Rav4 was traveling northbound on Route 29 north of Broken Land Parkway when it left the roadway for an unknown reason and struck a barrier. The driver and sole occupant, 71-year-old Mark Richmond of Ellicott City, was transported to Howard County General Hospital where he was pronounced dead. Preliminarily, police believe Richmond might have suffered a medical emergency before the collision. The investigation is ongoing.