An assembly includes a bed having a reclined position in which the bed is elongated along an axis A. The bed includes a first side and a second side with the axis A between the first side and the second side. The bed in the reclined position has a first end and a second end spaced from each other along the axis A. The bed includes an occupant support surface between the first end and second end. The assembly includes an airbag that is inflatable from an uninflated position to an inflated position. The airbag is housed in the first end in the uninflated position. The airbag in the inflated position has an arch shape between the first side of the bed and the second side of the bed. The arch is elongated along the axis A from the first end toward the second end above the occupant support surface.