A long, inflatable tube wrapped in a woven fabric sleeve is concealed beneath the A-pillar molding and the outer edge of the headliner. The tube is anchored at the base of the A pillar and at the roof above the rear door.
In a side-impact accident, an airbag-style inflator fills the tube with gas. The device is triggered by a side-impact crash sensor mounted on the car's driveshaft tunnel near the rear seats. The inflator is mounted beneath the dashboard.
As the tube inflates, its woven covering contracts and pulls the device out of the headliner so that it stretches diagonally across the window opening.
BMW says the shape provides protection for short people who sit close to the instrument panel as well as taller people who sit farther back.
BMW will install the system only in conjunction with its door-mounted side-impact airbags. That will give the 1998 BMW 7 series six inflatable restraints - two frontal airbags, two door-mounted airbags and two head-protection bags.