The maximum travel distance from the most remote point in any room or space to the center of a door opening directly on an open exterior space, a vertical exit, an interior stair, an exit passageway or to a horizontal exit shall not be greater than the limit specified in table 6-1 for the occupancy group classification of the room or space.
(b) Travel distance within dwelling units. In buildings classified in occupancy groups J-1 and J-2, the maximum travel distance from the centerline of a door from any habitable room within a dwelling unit either to the centerline of a door opening on a corridor or to the center of a door opening on an exit shall not be greater than forty feet, except that for buildings classified in occupancy group J-2 of construction class I-A, the distance may be increased to fifty feet. Such travel distances shall be included in the maximum travel distance established in subdivision (a) of this section.
(c) Measurement. Travel distance shall be measured along a natural and unobstructed path of travel. Where the path of travel is over an access stair, it shall be measured along an inclined straight line through the center of the outer edge of each tread.