What is the legal rule regarding carrying luggage or goods in the passenger aisle (Mittelgang) of a passenger coach?

1. Luggage can be stacked up to the ceiling in the aisle if straps are used
2. Aisles can be blocked as long as passengers can climb over the bags
3. The center aisle and all emergency exit pathways must remain completely free and unobstructed at all times; storing luggage, boxes, or folding chairs in the aisle is strictly prohibited
4. Aisles are designated for heavy freight transport