The New Mercedes-Benz E-Class Cabriolet: Active Safety
Engineers in Sindelfingen are dedicated to advancing the development of assistance systems which warn and assist the driver
by Chris Danielson | 09 March 2010
Preventing traffic accidents is at the heart of Mercedes-Benz’s commitment to safety. This is why the engineers in Sindelfingen are dedicated to advancing the development of sophisticated assistance systems which warn and assist the driver in critical driving situations and can act autonomously if there is acute danger. ABS, ESP® and BAS (Brake Assist) were the first technologies of this kind; their positive effect has since been confirmed by an analysis conducted by the Mercedes Accident Research department based on anonymous data samples from the German Federal Statistical Office.
The new or modified driver assistance systems in the E-Class Cabriolet are based on state-of-the-art radar and sensor technology. They have been developed to help reduce the number of accidents caused by being too close to the vehicle in front, drowsiness and darkness.
The driver assistance systems for the new
E-Class Cabriolet at a glance:
|ABS||Standard: ensures that the car remains steerable, even when braking.|
|ESP®||Standard: reduces the risk of skidding and stabilises the car.|
|Brake Assist (BAS)||Standard: provides full braking power within a fraction of a second in the event of an emergency stop.|
|Adaptive Highbeam Assist||Optional: this system adjusts the range of the headlamps in accordance with the distance to oncoming vehicles/vehicles travelling ahead and switches high beam on/off.|
|Adaptive brake lights||Standard: the brake lights flash to warn drivers behind more effectively if the brakes are applied in an emergency.|
|ATTENTION ASSIST||Standard: is able to recognise signs of drowsiness based on sensor signals, and warn the driver.|
|Intelligent Light System||Optional: incorporates five light functions specially configured for typical driving situations and weather conditions.|
|DISTRONIC PLUS||Optional: uses radar to help the driver maintain the desired distance between the E-Class and the vehicle in front, and can warn the driver if the gap narrows rapidly.|
|Brake Assist PLUS (part of DISTRONIC PLUS)||Optional: can use radar sensors to detect an imminent head-to-tail collision, calculate the level of braking assistance required and provide this assistance instantaneously when the brake pedal is pressed.|
|PRE-SAFE® Brake (part of DISTRONIC PLUS)||Optional: can initiate partial or emergency braking automatically if a head-to-tail crash is imminent and the driver fails to react.|
|Parking aid||Optional: ultrasonic sensors measure the length of parking spaces as the car drives past; instructions for precise parking appear on the display.|
Preventive protection measures: PRE-SAFE® now also includes AIRCAP
In the new E-Class Cabriolet, occupant protection actually begins in the phase leading up to a possible accident thanks to the Mercedes-Benz PRE-SAFE® invention, which is specified as standard for the two-door model. In the event of critical driving situations with a high risk of an accident, the system activates protective measures as a precaution, allowing the seat belts and airbags to deploy with maximum effect in the event of any subsequent collision. This early accident detection is possible because PRE-SAFE® is an intelligent synergy of active and passive safety. It is linked to Brake Assist and the Electronic Stability Program (ESP®), for example, whose sensors can detect critical driving situations and send the relevant information to the electronic control units within a matter of milliseconds. PRE-SAFE® also uses these sensor data.
Anticipatory occupant protection can be activated in the event of emergency braking or critical lateral acceleration as well as when imminent danger is detected by the sensors of the assistance systems alone. The AIRCAP® automatic draught-stop is likewise integrated into the PRE-SAFE® system. If the system detects a risk of roll-over, AIRCAP® is retracted as a precaution.
|PRE-SAFE® in situations with critical longitudinal dynamics||PRE-SAFE® in situations with critical lateral dynamics*|
|Driver and front-passenger seat belts are tensioned by means of electric motors||The front side windows are closed|
|Electrically adjustable front-passenger seat** is moved backwards or forwards into a better position from an accident standpoint whilst the cushion angle and backrest inclination are also optimised. The side bolsters of the multicontour seat are inflated**||The front wind-deflector module of the AIRCAP® system** is retracted|
*In addition to the emergency-braking measures**Optional equipment
First Mercedes-Benz Cabriolet with headbags
- Exemplary occupant protection with sophisticated restraint systems
- Robust rear roll-over bars triggered by pyrotechnic means
With seven standard-fit airbags, belt tensioners and belt force limiters on all seats, as well as crash-responsive head restraints for the driver and front passenger, the new E-Class Cabriolet offers the most comprehensive array of safety features in this vehicle category. The range of airbags, which can deploy in thousandths of a second in an accident, comprises front and side airbags for the driver and front passenger, a kneebag for the driver and, for the first time in a Mercedes-Benz Cabriolet, headbags.
Whereas windowbags are used in cars with a conventional, fixed roof, mostly housed in the roof frame, the Mercedes-Benz safety specialists naturally had to employ a different airbag as well as choose a different installation position in the case of the E-Class Cabriolet. Here headbags are integrated into the door panelling in the beltline area. Covering a wide area – around 0.7 x 0.5 metres with a volume of 17 litres when deployed – the airbags provide extremely effective protection for occupants large and small in the event of a crash. The side protection system – comprising headbag and thoraxbag – optimises the level of protection afforded to individual parts of the body. Rear sidebags are available as an option.
Exemplary safety combined with maximum comfort is the best way to describe the restraint systems in the E-Class Cabriolet. When front passengers get into the car and close the doors, the seat belts are extended towards them by means of belt feeders – a Mercedes-Benz hallmark – making the belts extremely easy to put on. Once the rear passengers have taken their seats and belted up, the rear head restraints are raised from their recessed rest position to the driving position automatically. If only the front seats of the Cabriolet are occupied, there is always excellent rear visibility, while any rear passengers on board benefit from the protective effect of the head restraints in the event of a crash, providing they are wearing their seat belts.
What’s more, the geometry of the front seat belts has been optimised. The belt straps no longer run horizontally but, instead, are turned 35 degrees towards the occupants’ shoulders. The advantage of this modification is that the wind pressure on the outside of the belt strap prevents annoying belt flapping when driving with the roof down. This dreaded “shoulder-knocking” effect has been reduced substantially at speeds of up to 120 km/h.
Robust roll-over bars triggered by pyrotechnic means
Further safety features for the open-top two-door model include the A-pillars reinforced by two additional tubes, the plug-in B-pillars and roll-over protection. The latter consists of two robust bars, each with a diameter of 35 mm, which are housed in the rear head restraints in modules behind the rear seat backrests. If the sensors housed in the airbag control unit detect imminent danger to the occupants, pre-tensioned pressure springs are activated by pyrotechnic means, i.e. extremely quickly.
Consequently, both roll-over bars in the rear head restraints are extended. They reach their highest point and are locked automatically within a fraction of a second. In combination with the robust A-pillars, each of which is reinforced with two high-strength steel tubes, the steel bars provide highly effective roll-over protection.
Under the microscope
To be on the safe side: over three dozen different crash tests
Safety pioneer Mercedes-Benz has been conducting routine crash tests on complete vehicles since the late 1950s. Béla Barényi established systematic safety testing. The first crash tests were spectacular, with cable winches or steam rockets being used to propel the cars. Today the cars are accelerated by a hydraulic catapult.
The number of different crash tests has risen dramatically over the years because, in keeping with its holistic “Real Life Safety” approach, Mercedes-Benz does not only perform crash tests using those crash configurations that are specified for rating tests and world-wide approval. It also conducts crash tests based on the in-house accident research department’s findings, whose requirements sometimes go way beyond those of the statutory requirements. New Mercedes passenger cars therefore have to pass a total of over three dozen different crash tests. Currently, some 500 crash tests per year take place at the Mercedes safety centre in Sindelfingen, plus more than 50,000 computer-simulated tests.
One of the most demanding in-house crash tests is the roof-drop test, which Mercedes-Benz uses to check the body’s roll-over protection. The new E-Class Cabriolet also had to pass the roof-drop test with extreme load on the roof frame. Here the body is dropped onto its roof at a slight angle from a height of 50 centimetres. Consequently, the vehicle lands with its full weight on one of the two A-pillars, which is only allowed to deform slightly if the vehicle is to pass the tes