achieve these objectives is dependent partly upon the thickness t and the characteristics of the viscoelastic cushion 12 as explained above the preferred cushion 12 is formed from a viscoelastic foam with a density in the range of 50 120 kg m 3 with a preferred density of about 85 kg m 3 additionally the preferred viscoelastic material has a hardness or firmness of about 10n viscoelastic materials with these specifications and with a thickness t of about 1 inch have proven to provide high levels of comfort with little or no sensory evidence of the gap 108 hard structural supports of the seat 100 or the vibrations of the vehicle regardless of whether the seat 100 is erect reclined or partly reclined in this regard the density firmness resiliency and thickness of the viscoelastic cushion 12 enable lower surface 12 l of the viscoelastic cushion 12 to flow into and conform to the gap 108 and other pinch points as shown in fig1 thereby creating a convex lower conformal area 12 lc and a substantially smooth uniform upper surface 12 u for facing the traveler the cover assembly is sufficiently stretchable and or loose to permit the viscoelastic material 12 to flow or conform substantially unimpeded into the potential pinch points and around hard points furthermore the density hardness firmness resiliency and thickness characteristics of the viscoelastic cushion 12 ensure that weight of the traveler will create a concave upper conformal area 12 uc that will be spaced above the lower surface 12.