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Active and passive safety: Surely one of the best SUVs around

Jul 15, 2008
During development of the active and passive safety elements in the new GLK, Mercedes-Benz took its cue from the findings of the company's own accident research programme, which was initiated over 60 years ago and has made a decisive contribution to the ongoing evolution of automotive safety. Apart from
this wealth of experience, development also draws on the latest findings from investigations into actual accidents, as well as detailed simulations and exhaustive testing, then translates it all into concrete protective measures.
The all-encompassing approach taken to achieving a high standard of safety evinces itself particularly clearly in the Integral Safety concept, that Mercedes-Benz has once again implemented in the new GLK. This groundbreaking safety philosophy goes far beyond just compliance with crash test specifications. Instead, it concerns itself with all aspects of motoring – everything that is of relevance for the safety of both the vehicle's occupants and other road users. The Mercedes safety concept divides these different aspects into four phases:
1. Safe driving:
avoiding danger, warning and rapid assistance
2. When danger threatens:
acting in an anticipatory manner with PRE-SAFE®
3. During an accident:
protecting as required
4. Following an accident:
damage limitation, rapid assistance
Comprehensive restraint system for the best possible occupant protection
In combination with the front and rear deformation zones, the high-strength passenger cell of the GLK-Class provides a highly efficient foundation for the occupant protection systems. The intricate restraint system is capable of offering the greatest possible protection potential. As many as nine airbags are fitted, which are deployed selectively depending on the type of collision and its severity to reduce the forces exerted on the occupants. The individual components include:
  • Adaptive, two-stage airbags for the driver and front passenger
  • Kneebag for the driver (Europe)
  • Front sidebags and, as an option, sidebags for the rear seats
  • Windowbags across both seat rows from the A-pillar to the C-pillar
  • NECK-PRO crash-responsive head restraints for the driver and front passenger
  • 3-point seat belts for all five seats
  • Belt tensioner and adaptive belt-force limiter for the driver and front passenger, belt tensioner and single-stage belt-force limiter for the outer rear seats
  • ISOFIX child seat attachments
  • Belt height adjuster for driver and front passenger
  • Belt status indicator for the rear passengers in the instrument cluster
  • Automatic child seat recognition (optional) which deactivates the front passenger airbag when a specially designed Mercedes-Benz child seat is used
ARAMIS: central control unit for the restraint systems
In the GLK, the task of deploying the driver and front-passenger airbags, kneebag, sidebags, windowbags, belt tensioners and NECK-PRO crash-responsive head restraints in line with the type of collision and its severity is handled by the central control unit, dubbed ARAMIS. This electronic safety "command centre" is able to detect the impact type and severity in a matter of milliseconds, then trigger the restraint systems as required on the basis of the calculated prognosis of the impact's severity. The ARAMIS control unit gleans the necessary information from an elaborate network of sensors, including two up-front sensors on the flexible bumper bracket at the front, two lateral satellite sensors near the base of the B‑pillars, as well as supplementary pressure sensors in the doors. In addition to this, ARAMIS can activate individual functions which are able to defuse an accident situation following the actual impact: certain portions of the vehicle's electrical network can be isolated from the battery, the engine shut off, the hazard warning lights and crash-responsive emergency lighting switched on, the doors unlocked, and the side windows lowered by 50 mm.
High-strength passenger cell, energy-absorbing front and rear-end structures
The excellent protective abilities of all GLK models are underpinned by a unitised sheet-steel body featuring a high-strength passenger cell together with front and rear-end structures that fulfil a deforming function in the event of a crash, enabling as much of the impact energy as possible to be absorbed
The following measures have been implemented at the front end of the body to ensure outstanding energy absorption. In all, the individual assemblies and components involved form three separate paths for absorbing and channelling the energy released by the impact:
  • A frame-type integral support made of high-strength steel, which incorporates parts of the wheel location componentry, the rack-and-pinion steering gear and the engine mounting, directs forces straight into the floor structure. In particularly severe frontal collisions, the frame-type integral support itself crumples to absorb additional energy.
  • Mid-level collision plane comprising longitudinal members that have been optimised both in terms of the material they are made from and their design.
  • Purpose-designed wheel arch reinforcements form a third supporting structure above the front longitudinal members which further boosts resistance to deformation in the event of collisions from the front.
  • A strut made from ultra-strength steel running between the shock absorber tower and the windscreen cross member on the driver's side serves to disperse the forces originating from the top longitudinal member plane, as well as limit the amount by which the steering and pedals are pushed backwards.
  • Additional impact-absorbing elements in the extension of the longitudinal members together with purpose-designed pedal-floor cross members are able to protect the footwells on the driver and front passenger sides.
  • Reinforced firewall members which are able to reduce penetration of the front wheels into the footwells in a heavy frontal collision, especially when there is an offset to one side.
The passenger cell forms the hard core of passive safety, enveloping the vehicle's occupants in a high-strength safety cage. This exceptional degree of stability is attained as follows:
  • increased use of high and ultra-high-strength sheet steel, as well as tailored blanks with partially graduated wall thicknesses
  • transversely rigid floor assembly, featuring additional reinforcement sections between the longitudinal members at the front and sides and the propshaft tunnel
  • a continuous cross member for the rear seats
  • cross member in the form of an extruded aluminium section extending between the A-pillars underneath the dashboard
  • transversely rigid bracing of the load compartment using a cross member beneath it
  • transversely rigid seats resulting from the use of tubes and impact-absorbing elements in the side seat trim sections.
There are amply proportioned deformation paths for absorbing impact energy at the rear end of the body. The rear longitudinal members are made from high-strength steel in the critical crumple zones. The fuel tank is in a well-protected location, underneath the rear bench seat and in front of the rear axle.
Standard of pedestrian protection sets an example for the SUV segment
During the development phase of the GLK, particularly close attention was paid to pedestrian protection. This is why standard equipment for all GLK models includes Brake Assist (BAS), which shortens the braking distance significantly when an emergency braking situation is detected, so as to help prevent accidents or at the very least mitigate their consequences. Secondly, the front section incorporates precisely defined clearances between the body and the major assemblies beneath, allowing the bonnet to yield considerably if hit by a pedestrian. This combines with the specially shaped design of the front bumpers and the softer foam used for their integral impact dampers to unlock further potential for protecting pedestrians.
World premiere: PRE-SAFE® makes its debut in a compact SUV
The optionally available PRE-SAFE® anticipatory occupant protection system, being made available in the compact-SUV market segment for the very first time, sees Mercedes-Benz taking safety in this segment to an unprecedentedly high level. The highlight of this safety concept, that has been the subject of ongoing development since it was first launched in 2002, is the networking between the active and passive safety systems. By using the information received from the sensors of the dynamic handling control systems – for example, BAS and ESP® – PRE-SAFE® is able to detect critical driving situations where there is a heightened risk of an accident occurring and take precautionary measures to protect the occupants.
PRE-SAFE® basically springs into action when one of the following criteria is met:
  • Emergency braking: sudden operation of the brake pedal that either triggers the Brake Assist (BAS) or summons up over 70 per cent of the maximum possible braking pressure.
  • Heavy understeer or oversteer
  • Critical steering movements at high speeds, which indicate a startled response on the part of the driver and can destabilise the vehicle.
  • The driver increases the force applied at the brake pedal while already braking (post panic braking), signalling a wish for a higher rate of deceleration than that which is physically possible. This can be the case when aquaplaning, for instance, or when driving over ice or snow.
When a potential accident situation is detected, the system primes both the occupants and the vehicle for a possible impact. To this end, the seat belts for the driver and front passenger can be pulled taut if necessary. The optionally available power adjustable front passenger seat with memory function can be brought into a more favourable position that maximises the protective capabilities of the airbags and seat belt system. The system also takes the precaution of closing the panoramic glass sliding sunroof and side windows if a critical driving state affecting the vehicle's lateral dynamics arises. This optimises the protective effect of the windowbags on the one hand, whilst also better preventing foreign objects from penetrating the interior or parts of the body from dangling dangerously outside.
If a collision is averted and a stable driving state restored, the seat belts will slacken again. All other systems that have been triggered – such as the repositioned front passenger sear, side windows and sliding sunroof – can be returned to their original position.
Outstanding active safety courtesy of the AGILITY CONTROL suspension, 4MATIC all-wheel drive and pioneering dynamic handling control features
Whereas the passive safety systems enable a high degree of occupant protection during and following an accident, the active safety features are designed to take action beforehand. The high standard of active safety in the GLK-Class is rooted in the AGILITY CONTROL suspension with selective damping system, which blends stable handling with comfort. The electrohydraulic AGILITY CONTROL steering that comes as standard keeps the driver perfectly informed of the current state of the road, whilst responding with utmost precision to steering inputs. The V6 models – the GLK 320 CDI 4MATIC, GLK 350 4MATIC and GLK 280 4MATIC – benefit from speed-sensitive power steering as standard for even greater operating convenience.
The sophisticated 4MATIC all-wheel drive system, with its stable, safety-enhancing basic set-up, as well as the standard dynamic handling control systems – ESP®, 4ETS and ASR – come to the driver's aid in critical driving situations. The same is true of the ADAPTIVE BRAKE system, featuring built-in functions such as hill-start assist, priming of the brake system for more spontaneous response in the event of panic braking and braking the brake discs dry in the wet. The tyre pressure loss warning system forms part of the basic specification too, as does the ESP® trailer
stabilisation function. There is also the option of the tyre pressure monitoring system, which monitors the individual tyre pressures and notifies the driver of exactly which tyre is not inflated to the correct pressure.
Excellent driver-fitness safety for tremendous peace of mind
A high level of driver-fitness safety is an intrinsic component of any passenger car model from Mercedes-Benz. Relaxed, fatigue-free driving, even over long distances, is helped by the sense of wellbeing aboard the vehicle that Mercedes is renowned for. This is down to aspects such as the outstanding seat and ride comfort, a pleasant level of background noise and ergonomic controls, along with a climate control system that can be sensitively adjusted to suit requirements. The tinted glass all round and the optional LINGUATRONIC voice-operated control system make travelling in the GLK a true pleasure. Driver-fitness safety also benefits from the wonderfully assured handling, as well as the cruise control with its integral SPEEDTRONIC variable speed limiter.
Features which contribute to the outstanding perceptive safety include the superb all-round view, the extensive swept area of the front windscreen, as well as the generously sized, heated and electrically adjustable exterior mirrors. Perceptive safety is given a further boost by the powerful H7 headlamp system with integrated cornering light function and Headlamp Assist. For even greater visibility at night, there is the option of the Intelligent Light System (ILS) with bi-xenon headlamps. Also helping to prevent accidents are the standard-specification adaptive brake lights, which flash when the brakes are applied in an emergency as a warning to road users behind and thereby serve to heighten safety in general in critical driving situations. The driver's perception of the vehicle's surroundings can be further enhanced by the addition of equipment features such as the rain sensor with two different sensitivities that can be set using the control stalk, the PARKTRONIC manoeuvring aid or the reversing camera.