Roof-mounted occupant restraint system

A restraint system for helping to protect an occupant of a vehicle having a roof and a cabin with a seat for the occupant, comprising:

• an airbag having a stored condition within the roof and being inflatable to a deployed condition extending into the cabin and aligned with the seat;
• a one-piece tether having a first end connected to a lower portion of the airbag and a second end connected to the roof;
• and
• tear stitching interconnecting overlying portions of the tether, the tear stitching being rupturable in response to occupant penetration into the deployed airbag to permit the interconnected overlying portions to move relative to one another such that the tether lengthens from a first length prior to occupant penetration to a second, longer length in response to occupant penetration, wherein the tear stitching is configured to rupture gradually in response to occupant penetration so that the lengthening of the tether due to rupturing of the tear seam is commensurate with the magnitude of forces exerted by the penetrating occupant so as to provide a gradual ride down for the penetrating occupant, and wherein the tether is connected to an upper portion of the airbag and wherein the lower portion of the airbag is configured to deploy into engagement with at least one of a lower torso and lap of the occupant so that the occupant fixes the lower portion of the airbag in place, allowing the tear stitching to rupture and the tether to unfurl in response to occupant penetration.