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During the development process for the new SL the requirements of Euro NCAP and other rating institutes were taken into account. The basis for this is a new light-alloy bodyshell which is formed mainly by extruded sections and cast nodes made of aluminium. It facilitates a light yet stable cell compound for a highly rigid occupant cell. In conjunction with this the tail end and front are designed in such a way that in the event of an accident they can absorb high forces through deformation, thus considerably reducing the strain on the occupants in a crash in accordance with the principle of the crumple zone. The crash boxes behind the bumper trim and an exchangeable front module ensure that the damage sustained during a front impact at up to 15 km/h can be limited.
Protection in the event of an overturn
The occupants in the new SL enjoy good protection in the event of a potential overturn, too. A-pillars in a steel/aluminium material mix and two roll-over bars can protect the passenger compartment. Normally the two roll-over bars are completely recessed, so they do not interrupt the look of the elegant, luxury roadster’s flowing lines. They are located in two cartridges fixed to the bodyshell in the area behind the seat backrests. If the system of crash sensors detects a potential overturn, the airbag control unit emits a signal and the deployment mechanism is activated. Two preloaded pressure springs per cartridge see to it that the roll-over protection shoots to the support position in fractions of a second.
Headbag and crash-responsive head restraints
The restraint systems with two-stage driver and front passenger airbags have been enhanced. A headbag provides generous lateral protection for the head impact area. An additional thorax airbag in the seat backrest can protect the upper body in the event of a side impact. The seat belts, with inertia-reel tensioners and belt force limiters, serve to highlight the high safety standards of Mercedes-Benz.
Another new feature finding its way into the standard equipment of the SL comes in the form of the NECK-PRO crash-responsive head restraints, developed by Mercedes-Benz. They can support the driver’s and passenger’s head in the event of a rear impact and reduce the risk of whiplash. Also fitted as standard is automatic child seat recognition. The ISOFIX child seat fastening system is available as an optional extra.
The latest technology for pedestrian protection
The new SL-Class Roadster uses the latest technology in the area of pedestrian protection, too. A sensor system is able to register an impact with a pedestrian and can ensure that the bonnet is immediately raised by 85 mm in the rear section. This creates additional space between the bonnet and the components in the engine compartment. This in turn results in comparatively lower acceleration values for the head of a pedestrian during the impact, thus reducing the overall risk of injury.
The deformation properties of the bonnet have also been specifically designed to meet the requirements concerning pedestrian protection. It consists of aluminium with a homogenous reinforcement on the inside of the bonnet and can therefore further reduce the loads in case of an accident. The SL’s "soft nose" also provides a large impact area, whilst the foam density and geometry in the front bumper have been optimised for reduced loads during leg impact with the pedestrian.
Only available from Mercedes-Benz – the anticipatory occupant protection system PRE-SAFE®
An additional safety highlight is the standard-specification anticipatory occupant protection system PRE-SAFE®, a system developed by Mercedes-Benz and unique throughout the world. If it detects an acute risk of an accident, it reflexively activates precautionary protective measures for the vehicle occupants, also including the reversible, electromotive belt tensioning function which ensures that the occupants are better secured so that the seat belts and airbags are able to perform their protective function to the full during an impact. Mercedes-Benz developed PRE-SAFE® on the basis of research into actual accidents, and is the only manufacturer in the world to offer such a system.
Following an accident – optimally prepared
Mercedes-Benz’s holistic safety concept involves taking the phase after an accident into account. This is why the new SL has numerous post-crash measures incorporated on board which facilitate rapid assistance should the worst come to the worst: depending on the type of accident and the impact severity, the doors can be automatically unlocked, the interior lighting activated and the side windows opened by 50 millimetres to provide better ventilation in the interior. In addition to this, the steering wheel can be slid upwards. The concept is completed by the Guidelines for Rescue Services and the rescue cards which can be downloaded from the internet free of charge and which can serve as a valuable support for fire brigades.
ATTENTION ASSIST and ADAPTIVE BRAKE as standard
The new SL also features a unique combination of driver assistance systems which help to avoid accidents. These include the standard ATTENTION ASSIST, for example. Thanks to this system, the Roadster develops a precise feeling for the level of attentiveness of the driver and can provide an early warning of overtiredness.
Also making up part of the standard equipment specification is the ADAPTIVE BRAKE. It comprises ABS, the acceleration skid control system ASR and also active yaw control (GMR). In addition, it features the following functions:
- it supports the driver when moving off uphill, by preventing the vehicle from unintentionally rolling back;
- it also keeps the vehicle stationary without having to keep the brakes applied continuously – for example when waiting at traffic lights;
- as soon as the driver abruptly steps off the accelerator, it brings the brake pads into light contact with the brake discs as a precautionary measure, so that the necessary braking pressure can be attained quicker in the possible event of emergency braking;
- in wet conditions it applies light brake contact, without the driver even noticing, to dry the brake discs
The ADAPTIVE BRAKE works in conjunction with the equally adaptive brake lights. In emergency braking situations, it warns vehicles behind with rapidly flashing brake lights.
PRE-SAFE® Brake: autonomous partial and emergency braking in response to a serious risk of a rear-end collision
Available as optional extras are the DISTRONIC PLUS proximity control as well as the PRE-SAFE® Brake, already tried and tested in other Mercedes-Benz models. The two systems together and can initiate emergency braking automatically on detecting an acute risk of an accident.
In normal driving conditions, the radar-based DISTRONIC PLUS proximity control adjusts the distance to the vehicle in front automatically. If necessary, it can apply the brakes, even bringing the SL-Class Roadster to a stop, and accelerate it again. This takes some of the strain off the driver, particularly in bumper-to-bumper driving conditions. If the distance starts to narrow too quickly, the system gives the driver visual and acoustic warnings, thereby prompting the driver to take action, at which point they are also supported by Brake Assist PLUS (BAS PLUS).
If the systems detect the acute danger of a rear-end collision and the driver fails to respond to visual and acoustic warnings, the electronics activate the PRE-SAFE® Brake in preparation for autonomous braking. This happens in three stages:
Around 2.6 seconds before the calculated impact, the driver receives three audible warnings; around 1.6 seconds before the calculated accident, the car initiates autonomous partial braking with around 40 percent (approx. 4 m/s²) of the maximum braking power, gives the driver an additional, haptic warning of the impending impact and as a precaution activates the reversible PRE-SAFE® occupant protection systems.
If the driver still fails to react, the PRE-SAFE® Brake activates the maximum braking power around 0.6 seconds before the now unavoidable collision – this emergency braking can greatly reduce the severity of the impact. The system therefore acts like an “electronic crumple zone”, offering the car occupants even greater protection.
The PRE-SAFE® Brake is active at speeds of between 30 and 200 km/h when moving vehicles are detected in front of the car. The system also reacts if the car approaches a stationary queue of traffic, providing its speed is below 70 km/h.
The functionality of DISTRONIC PLUS has been enhanced even further. It now reacts earlier to vehicles which cut in, and the car accelerates quicker when changing lanes itself and where the overtaking lane is clear. Thanks to the incorporation of information from digital maps (navigation mode), automatic control has also been further refined.
Intelligent Light System – good vision at all times
The Intelligent Light System also comes as part of the standard specification. It offers variably controllable headlamps with five different light functions which are adapted to suit driving and weather situations commonly encountered. They switch themselves on depending on the prevailing driving situation, offering the motorist a considerably greater field of vision:
- the country mode distributes the light from the low-beam headlamps in such a way that the left edge of the carriageway is illuminated more brightly and across a larger area
- the motorway mode switches on from a speed of 90 kilometres per hour and enlarges the field of vision by as much 60 percent
- the cornering light function is automatically activated when the main headlamps are on and if the driver operates the indicator or turns the steering wheel at a speed below 40 km/h. The low-beam headlamps and fog lamps then illuminate the side area ahead of the vehicle to a range of around 30 metres at an angle of up to 65 degrees
- the active light function improves illumination of the road on bends by up to 90 percent
- the enhanced fog light function works by pivoting the left-hand bi-xenon headlamp outwards by several degrees and lowering its beam. This provides brighter illumination of the inner half of the road
Adaptive Highbeam Assist is also on board as part of the standard specification: when vehicles are detected ahead of or approaching the vehicle, this system automatically dips the beams and adjusts the range of the headlamps according to the distance.
Assistance systems spring into action
Those wanting to can choose to extend the package of assistance systems in the new SL even further. They provide extra doses of both safety and comfort. As an option Mercedes-Benz can equip the roadster with the following helpful features:
- Speed Limit Assist: it is able to detect speed limit signs using a camera on the inside of the windscreen and indicate the respective detected speed limit on a display in the instrument cluster and in COMAND (standard-fit in conjunction with COMAND Online).
- Active Blind Spot Assist: it warns the driver when changing lanes if a risk of collision is detected due to another vehicle in the neighbouring lane being in the blind spot of the exterior mirror. If the driver ignores the warning and nevertheless initiates the lane-changing manoeuvre, the Active Blind Spot Assist intervenes. A brake actuation counteracts the collision course (part of the driver assistance package with DISTRONIC PLUS including the PRE-SAFE® Brake and Active Lane Keeping Assist).
- Active Lane Keeping Assist: this system kicks into action if the Mercedes-Benz vehicle inadvertently drifts over a solid line to the right or left of a lane. In such a case, a warning sign in the instrument cluster and vibrations in the steering wheel warn the driver. If the driver does not heed the warning in the case of a solid line, Active Lane Keeping Assist can use the ESP® to brake the opposite wheels and thereby prevent the vehicle from crossing the solid line (also part of the driver assistance package – please see above).
Hands off the steering wheel when parking
Active Parking Assist will answer the prayers of many drivers in the chronically congested traffic areas of Europe: the SL can not only detect parking spaces, but also help with the parking itself. This is made possible thanks to a combination of the new electromechanical steering system (please see the chapter on the chassis and suspension) and a series of ultrasonic sensors. This convenience system features the following functions:
- measurement of potential parking spaces lengthwise to the direction of travel – even in slightly curved bends – up to a drive-by speed of 30 km/h. The parking spaces must be at least one metre longer than the vehicle
- calculation of a suitable parking manoeuvre in order to park the vehicle parallel to the kerb
- automatic steering in order to perform this parking manoeuvre
- automatic steering in order to exit the parking space. This is only possible if the parking space was entered using Active Parking Assist
Two ultrasonic sensors take care of the search for suitable parking spaces lengthwise in the direction of travel. They are integrated in the front bumper, on the left and right. If the speed falls below 30 km/h, a "P" symbol in the instrument cluster signals to the driver that the active search for a parking place has been started automatically. If the system has found a potential parking space, an arrow indicates this alongside the "P" symbol. As standard, the arrow shows parking spaces on the passenger side. If the indicator on the driver’s side has been activated, it shows potential parking spaces on the driver’s side.
It is up to the driver to assess whether the free area designated by the system is indeed actually a parking space. Even during the parking procedure the responsibility remains with the driver, who must use the accelerator and brake pedals during parking. The Active Parking Assist takes care of the steering and for orientation it uses the two front ultrasonic sensors as well as four further sensors in the rear bumper. During parking, the roadster must not move faster than 10 km/h. The automatic parking manoeuvre is configured for a maximum of five turns (backwards-forwards-backwards-forwards-backwards). Once the vehicle is standing correctly in the automatically selected parking space, the system aligns the wheels.
The Active Parking Assist switches itself off as soon as the driver intervenes in the automatic turning of the steering wheel, if the system is turned off via the PTS button (PARKTRONIC sensor), both if the driver’s seat belt buckle or the driver’s door is open, or if there is a system error. Nevertheless the familiar PARKTRONIC function remains available without any restrictions.
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