TUPELO, Miss. (AP) — More National Park Service rangers will range on the Natchez Trace Parkway in unmarked vehicles.

The Park Service says it's buying more unmarked vehicles for traffic enforcement on the scenic and historic route through Mississippi, Alabama and Tennessee.

Chief Ranger Sarah Davis says the Park Service is ordering a variety of vehicles — including full-size SUVs and pickup trucks — in multiple colors.

Davis says the move is meant to crack down on speeding and drivers distracted by cell phones. It follows a six-month pilot program showing a sharp increase in the number of traffic stops.

Although the vehicles may look normal, District Ranger John Hearne says the number of red and blue lights activated once an officer wants to make a stop will "look like a police Christmas tree."