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Emergency braking assistants in the test: what do the systems really do?

Hans-Dieter Seufert
Emergency brake assistants tested
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I In an emergency the normal driver does not brake well. According to the accident researchers' data, in around 90 percent of the cases either too late, too weakly or not at all. On the other hand, even small cars only slow down sports cars, as in the past, but none of that helps if this braking potential is not used. This is why almost all new cars nowadays offer a passive brake assistant that automatically completes an emergency stop based on the speed and pressure of the pedal.

However, active emergency brake assistants that use sensors (laser, radar or Camera) not only independently recognize a critical situation and warn the driver, but - if things get very precarious - even brake completely autonomously. auto motor und sport together with the TÜV Süd checked in an exemplary, extensive test series.

More than a third of the accidents could be mitigated

To evaluate the systems, their autonomous braking and warning capabilities were also assessed on the basis of actual accidents (data from 2010) and their actual distribution. According to this, over a third of all accidents with personal injury can theoretically be alleviated or even completely prevented by an emergency brake assistant.

Borderline cases such as intersection accidents were not taken into account in the test, as the response of the assistance systems depends heavily on how much time the sensors have to detect the vehicle turning into it. In the urban area all systems showed at least satisfactory accident avoidance abilities, but in very different ways: The city emergency braking systems from VW almost always avoid a collision up to 30 km /h, but they do not give the driver any visual or acoustic warning beforehand.

Even the Ford Focus dispenses with a warning during its Active City Stop and also runs into a stationary obstacle at 30 km /h due to a very late autonomous braking with a high residual speed of 24.6 km /h.

Less constant Emergency brake assistant in the Honda Civic

The CMBS systemof the Honda Civic showed the most inconsistent braking behavior in the test. At less than 30 km /h, due to the gentle and rather weak autonomous deceleration, no impact was avoided, but an early warning enables the driver to react independently.

The radar-based and standard system of the Mercedes B-Class detects stationary objects and does not master autonomous emergency braking, instead it prompts the driver to intervene with a timed visual and acoustic warning. Experience shows that this can prevent the majority of possible accidents. As with all other systems tested, the brake pads are already applied by the car for immediate deceleration.

The Volvo system provides almost perfect support in urban areas. It warns very early, was able to prevent all accidents in the test and even enables emergency braking for pedestrians with the unfortunately very expensive driver assistance package (1,980 euros).

System of the VW Up ineffective at higher speeds

In the higher speed range (72 to 100 km /h) the system of the VW Up as the only ineffective. The entirely optional systems in Focus, Civic, S60 and Passat, coupled with adaptive cruise control, significantly reduce the impact speed with autonomous braking. The remaining speed in the Volvo and VW Passat is significantly lower than that of Honda and Ford. In the previous warnings, it is also noticeable that Volvo tends to warn early and VW rather late in the 72 km /h test. However, warnings that are too early can lead to annoyance and too late to put the driver in a mess.

It is even more annoying when the systems trigger incorrect braking. Even an unnecessary jolt of the brake, as in the VW Passat, for example, can shock inexperienced drivers such as the traffic behind them very much. Fortunately, this only happened very rarely in the test.

Unfortunately, emergency braking assistants are also rare - if they cost extra. Expensive systems - with the exception of Volvo - rarely find buyers. Just 1.5 percent of Focus buyers and 2.3 percent of Civic customers can afford this safety plus. The benefit for all traffic is correspondingly low. As the example of ABS and ESP shows, safety systems only significantly reduce the number of accidents if they are offered as standard. Volvo and Mercedes are setting a good example here .

This is how testing was done

The measurements of the emergency brake assistants were carried out by the TÜV Süd specialists on behalf of auto motor und sport . Eight different accident scenarios were created with a mobile universal obstacle also accepted by Euro-NCAPplayed through. The four most significant are shown as examples on the following pages. During the test, a centimeter-accurate differential GPS system measured the exact deceleration and position of the test car and obstacle. A camera inside the car also recorded the exact warning time of the emergency brake assistant.

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