Plenty more safety to come, says Mercedes

SIDE-impact bars that inflate like steel airbags in the doors, an underbody airbag that jams into the road surface to double braking force the moment before a crash and seats that move occupants away from the doors milliseconds before impact are just some of the next-generation crash safety ideas being trialled by Mercedes-Benz.

In all, more than a dozen breakthrough crash safety protection systems using 27 new patented devices have been packed into two Mercedes ESF (Experimental Safety Vehicle) 2009 test vehicles.

One of these was shipped to Australia and shown to the media at Mercedes-Benz Australia’s Melbourne headquarters last week by a team of the German manufacturer’s safety experts led by Mercedes-Benz Cars vice-president of development, engineering and safety, Ulrich Mellinghoff.

From top: Mercedes-Benz Experimental Safety Vehicle, active headlights illustration, inflating seat bolster, braking bag.

Described by Mr Mellinghoff as “guardian angels”, most of the new devices are triggered by radar detectors surrounding the car, giving vital moments to maximise protection of occupants in a collision.

Mr Mellinghoff said Mercedes-Benz had already “made the car more of a thinker” with devices such as electronic stability control, lane keeping assist, autonomous braking and Pre-Safe crash preparation systems, as it works towards its goal of accident-free driving.

But he said these new systems showed that major advances could still be made in occupant protection, not just crash avoidance.

Mr Mellinghoff predicted that up to 80 per cent of the ideas being trialled in the ESF 2009 would make it into production, as usual starting in top-end vehicles such as the next-generation S-class and then filtering down through the range.

He said that as with other Mercedes-Benz safety advances such as airbags, the company would allow other manufacturers to adopt its patented technologies in the interests of making motoring safer for everyone.

The S400 Hybrid-based ESF 2009 – the first such Mercedes experimental safety vehicle since 1974 – has world-first inflatable metal structures in the doors to improve side impact protection.

Using airbag-style pyrotechnic inflators triggered by 360-degree radar, the flattened steel tubes in the door can be inflated in a fraction of a second, ballooning and pushing out the door skin to help create more crush space in the side of the vehicle.

The gas, forced into the tube at a pressure of up to 20 bar, remains in the tube during impact, helping to defray the energy from the side collision. The bars are even lighter by 500g than conventional steel bars.

Inside the car, side bolsters in the seats also inflate, pushing the occupants towards the centre of the car and away from the doors.

Feeling like a nudge in the ribs, the inflatable bolsters not only provide valuable millimetres between the occupant and the impending side crash but also free up space for the side airbags to work more effectively.

Benz engineers told GoAuto that a perennial problem with side airbags was their ineffectiveness when passengers rested their shoulder or head against the door, such as when sleeping.

As well, front and rear occupants benefit from devices that spring between their heads to prevent a clash of heads. In the rear seat, this takes the form of a padded part of the console that shoots out from between the top of the seats. Of course, this can only be used in vehicles with two defined rear seats.

In the front, small airbags are inflated from the seat backs, providing a barrier between the heads of the driver and passenger.

In the event of an unavoidable frontal collision, radar triggers a braking airbag under the front of the car, using the weight of the vehicle to press a rubber skid pad down on the road to momentarily increase braking force from the usual maximum 1g to 2g.

Mercedes engineers say the additional braking force has the effect of adding an additional 180mm of crumple zone to the front of the vehicle in a 50km/h impact.

They say an additional benefit of the upward movement of the car as the airbag inflates is that it eliminates the diving motion of the car just before impact and also helps to “pretension” occupants – taking up any slack in their seatbelts – due to the sudden extra braking.

However, they also revealed that the success in the device is all in the timing – immediately before impact – as it lifts the front wheels from the road, meaning conventional wheeled braking is rendered ineffective for a time.

The ESF 2009 also has full emergency braking triggered by 360-degree radar that includes braking in a rear-end collisions.

Mercedes says that contrary to popular belief, it is better to have the brakes full on during a rear-ender, as it helps to mitigate whiplash caused by an unrestricted car shooting forward.

It says it is also better to brake the car after impact to prevent a secondary collision that might, for example, send a car into oncoming traffic for even more disastrous consequences. However, because the driver is inevitably shoved back in the car by up to 20cm, reaching the brake pedal can become difficult, so Pre-Safe 360 does it for you.

At the front of the car, the move to LED lights has paved the way for adaptive headlights that automatically adjust the distribution of light so that oncoming drivers are not blinded by darkening the lights points towards the oncoming vehicle, while maintaining bright light on the other side of the road for improved safety.

The system, using a camera and headlights with 100 LEDs, can even spotlight obstacles such as a pedestrian on the side of the road to alert the driver.

Other systems on the ESF 2009 include airbags that tailor more effectively to the size of occupants, inflatable rear seatbelts to overcome the difficulty of airbag protection for rear-seat occupants, a child seat (developed with Takata) that more effectively protects smaller occupants, side reflective elements to make the car more visible at night and a rear seat camera so parents can watch children without turning around.