A gusset includes a floor attachment end, a side wall attachment end and an intermediate section. The floor attachment end is fixed to a reinforced floor portion of a vehicle. The side wall attachment end is fixed to a vehicle side wall structure at a point spaced apart from a side wall structure of the vehicle. The intermediate section has a generally U-shaped transverse cross section formed from generally upwardly oriented first and second gusset portions interconnected at upper ends by a top gusset portion. The reinforcement member is disposed within the gusset at a location between the floor and side wall attachment ends of the gusset. The reinforcement member interconnects the first and second gusset portions.