The passenger cell of the new CLS has been shown to be a structure which is virtually immune to deformation and which keeps the occupant space intact, even at high impact speeds, regardless of whether the collision is head-on, from the rear or from the side, or whether the vehicle rolls over. The use of high-strength steel and thicker panels plays as important a role here as the installation of additional load-bearing members.

The main floor assembly thus consists of different sheet-metal plates that either undergo flexible rolling or are welded together by laser beam and subsequently shaped. Flexible means that the high-tensile steel can be processed in such a way that areas with different steel thicknesses can be produced within a single component. The middle blank forms the tunnel - the actual backbone of the passenger cell. Here the thickness of the custom-designed panels varies between 0.7 and 1.1 millimetres, and between 1.55 and 2.0 millimetres for the tunnel reinforcements, depending on the stresses and loads to which they are subjected.

The continuous floor side members, the insides of which are further reinforced with extra sections, are very important both for occupant protection and the rigidity of the bodyshell. Their front faces connect to the side members, thereby lengthening the load-bearing paths along which forces can be distributed in the event of an impact. At the rear, the floor side members extend as far as the crossmember beneath the rear seat unit to stabilise the entire floor structure.

The Mercedes engineers have also incorporated sturdy aluminium transverse sections - known as transmission tunnel braces - into the floor assembly. One is located beneath the transmission, and is designed to direct forces to the side of the vehicle facing away from the impact in the event of a side-on collision. The second forms a connection between the two side members. It likewise braces the floor assembly and is able to channel impact forces into the floor structure at an early stage following a side-on collision.