If you must make an emergency stop on the side of a roadway and your vision is obscured, you should place a warning signal:

If you must make an emergency stop on the side of a road where your view is obstructed, place a warning signal 10 feet behind your vehicle and another 100 feet in front of your vehicle. Depending on what the situation requires, you should also place a warning signal between 100 and 500 feet behind your vehicle.