27. The clearance in the part of the passenger compartment reserved for passengers, measured at the centre of the bus or minibus on the longitudinal axis and between the vertical axes, shall be not less than 183 cm.
That clearance shall be maintained over an area not less than 30 cm wide on either side of the longitudinal axis and for the full length of that axis; clearance may not be less than 152.5 cm along the lateral walls.