During emergency or panic braking with Brake Assist, PRE-SAFE® pulls the seat belts taut as a precaution to fix the driver and front passenger securely in their seats, increase the distance to the dashboard and reduce the forward movement of the front seat occupants during a crash. For this important PRE-SAFE® function, the front inertia reels in the C-Class are equipped with powerful electric motors which respond within milliseconds and take up any belt slack. During emergency or panic braking, PRE-SAFE® furthermore starts by bringing an unfavourably adjusted front passenger seat into a better position – provided the car is equipped with the electrically adjustable front passenger seat with memory function. The system corrects both the backrest and seat cushion angles as well as the height and fore-and-aft adjustment of the seat as required, bringing the front passenger into a position which is more favourable from the point of view of airbag effectiveness and which allows the shoulder belt to exert a good restraining effect. This also lowers the risk of sliding beneath the seat belt strap and sustaining injuries during a collision.

If there is a danger of skidding owing to heavy understeering or oversteering, PRE-SAFE® activates a further protective function: in these situations the side windows and sliding sunroof begin to close as a precaution. Closed side windows are better able to brace the windowbags which deploy during a side impact. This preventive measure also lessens the risk of the occupants being thrown from the vehicle or objects penetrating into the interior during a crash. The sliding sunroof is linked to PRE-SAFE® because accident researchers analysing rollover accidents frequently find that car occupants can be completely or partially thrown out of the vehicle through the open roof. Closing the sliding sunroof as a precaution also reduces the risk of objects penetrating into the interior.

· Frontal impact:

Compared to the previous series, which itself offered excellent protection, Mercedes-Benz has further enlarged the deformation zones and optimised energy flows again. Like the C-Class Saloon, the new Estate features four independently acting impact levels which enable forces to be distributed over a wide area while bypassing the passenger cell. In addition to the robust aluminium cross member in the front end and side members which extend well forward to direct impact forces into the side structure, firewall and transmission tunnel, these forces are for the first time absorbed by the subframe made of high-strength steel too. For this purpose it has been extended forward and connected to the newly developed floor side members via special support tubes. During a crash this enables the subframe to both deform in a predetermined manner and absorb energy, while also transferring high impact forces directly into the vehicle floor.

In order to purposefully support and guide the front wheels, Mercedes-Benz developed special struts and additional impact-absorbing elements in the wheel arches. These struts are arranged diagonally and prevent the passenger cell from dropping during a collision, enabling the C-Class to absorb the impact energy and protect its occupants even more effectively. As another new feature on the driver’s side, an X-strut connects the shock absorber tower with the robust cross member beneath the windscreen and supports it. During an impact, this strut reduces the rearwards displacement of the shock absorber tower and the main brake cylinder behind it, to which the pedals are attached. This strut made from ultra-high-strength steel therefore has a dual function: it both lessens the loads acting on the firewall and prevents the pedal cluster from being pushed into the interior.

Side impact:

As only a very small crumple zone is available during a side collision, Mercedes engineers were careful to ensure that the impact forces are distributed over a wide area. The quadruple-shell B-pillars and the side members along the vehicle's flanks (sills) are mainly responsible for this. Both components are partly manufactured from ultra-high-strength, hot-formed high-tech steel. The impact forces are transferred from the B-pillar to the opposite side of the vehicle first and foremost via the transversely rigid seat and the centre console. Accordingly, the seats of the C-Class are equipped with tubular sections and impact-absorbing elements in the side mouldings. A futher load dissipation path runs from the base of the B-pillars to the cross member under the seats and the transmission tunnel braces. The B-pillars are also able to transmit forces to the roof frame. At the middle level, the doors with their rigid beltline sections and bonded-in reinforcing panels form a sturdy integrated structure.

Rear impact:

An effective crumple zone is also included at the rear end of the new C-Class Estate. This basically consists of multi-piece side members and a bolted-in section that acts as a cross member capable of absorbing large forces and distributing them into the body structure. The fuel tank is located in a protected position beneath the rear seat unit.

Passenger cell:

While the different load-bearing structures at the front, sides and rear end of the Estate are designed to deform and absorb energy during an impact, the passenger cell acts as the "hard core" of the safety concept in the C-Class. Even in a serious accident it only deforms very slightly to maintain the survival space of the occupants intact. Mercedes engineers have achieved this both by making increased use of high-strength and ultra-high-strength steel grades with graduated wall thicknesses, and by developing an extremely strong floor assembly. This comprises two continuous side members, several transverse sections, as well as two transmission tunnel braces which are able to transfer forces released in a side impact to the unaffected side of the vehicle.

The plastic front bumper has built-in foam elements to absorb the impact energy in collisions at speeds up to four km/h. The flexible material automatically returns to its original form after the crash.

Bolted to the bodyshell, the front-end assembly mainly consists of an extruded aluminium cross member with two aluminium crash boxes . Their strength and energy absorption are precisely calculated to ensure that at an impact speed of up to 15 km/h against a rigid barrier, any deformation is limited to bolt-on front-end components. All the components of this module are bolted together, and can therefore be replaced without the need for laborious welding work.

The rear bumper has the same elastic deformation properties as its opposite number at the front, and remains undamaged in collisions at speeds up to four km/h.

The rear-end module consists of a solid, flexible cross member and a crash box, both made of steel and bolted to the body structure. This module almost completely absorbs impact energy at collision speeds up to approx. 15 km/h.