Preventing accidents through driver assistance systems

Jun 2018

Vehicle Technology

Just these few facts concerning Germany, which are more or less the same in many parts of the world, reinforce the need to make a lasting difference – for example in relation to accidents that occur at the end of traffic jams, which can pose significant risks to vehicle occupants. In particular, accidents involving heavy-duty goods transport vehicles consistently result in occupants suffering severe or fatal injuries. If a truck crashes into the back of a stationary or slowly moving car at a high differential speed, it is highly probable that the car will suffer extreme deformation. Several vehicles are often pushed into each other. If a truck drives into the back of another truck, the occupants of the impacting truck usually suffer the most serious injuries. Even a car crashing into the back of a stationary or relatively slow-moving truck often ends fatally for the car occupants.

Optimization measures aimed at reducing the incompatibility of vehicle structures can certainly help to a degree. However, physical limits are quickly reached as the differences in speed become greater. Given the sheer mass of heavy-duty commercial vehicles, passive safety measures for mitigating the consequences of an accident offer only limited potential. Effective improvements are therefore to be achieved primarily through the use of driver assistance systems that either prevent accidents or reduce their severity. This involves forcing distracted drivers to re-engage with the traffic situation in a speedy and appropriate manner and automatically initiating braking just before a collision becomes unavoidable. The potential benefits of this technology have been investigated many times in recent years. In 2016, commercial vehicle experts at strategy consulting firm Roland Berger published a study entitled “Automated Trucks – The Next Big Disruptor in the Automotive Industry?”, in which they predicted that intelligent driver assistance systems could reduce the number of rear-end collisions involving trucks by over 70 percent.

More awareness of the system limits

All automatic safety systems must meet high requirements at all times. If the systems activate unnecessarily in a way that irritates or unnerves drivers, drivers will lose confidence in them and, in the worst case, simply disable the systems. Full functionality is necessary in critical situations, while it must also be possible for drivers to override the systems at any time for legal reasons.

Equally as important as drivers understanding the systems’ functionalities is the driver being aware of and understanding the full performance range of the systems and, above all, the limits of this technology. After all, these systems cannot override the laws of physics. They cannot boost brake power any more than they can shorten vehicle braking distances on wet or slippery roads. But the technology does ensure that drivers are alerted to critical situations so that they can take countermeasures themselves or, if they fail to do so, the vehicle’s brakes are applied automatically.

If the driver reacts by turning the steering wheel to make an evasive maneuver without applying the brakes, for example, the system is generally disabled because the driver has reacted in a way that overrides the system. If the driver does not know enough about how the system works and what its limits are in situations like this, the driver could simply rely on the automatic braking function and steer the vehicle only to make an evasive maneuver without themselves simultaneously applying the brakes – a situation where lack of information can have deadly consequences.

Disabling the systems is a risky game

Many drivers involved in serious accidents that occur at the end of traffic jams are accused of purposely disabling their automatic emergency brake assist system. Reliable, statistical data on this is not available but would be very desirable for the purposes of accident research. A questionnaire for truck drivers conducted by DEKRA Accident Research suggests that only a very small number of systems are disabled. However, it is striking that the AEBS is often taken to be the same as adaptive cruise control (ACC). While an AEBS brakes only when a collision would otherwise be unavoidable, adaptive cruise control brakes the vehicle as soon as the distance to the vehicle ahead is shorter than the minimum set distance. These braking functions are considered irritating when an overtaking vehicle pulls in ahead of you. If both systems are disabled because of lack of knowledge, any safety benefits offered by the AEBS are lost.

There are undoubtedly cases and situations where it is necessary to disable the systems briefly – particularly older AEBS. With the current generation of systems, however, this is rarely necessary because optimized technology has eliminated many sources of error. DEKRA emphatically supports the call for systems to be automatically enabled after a few seconds.

Seat belts are still important

Whether Electronic Stability Control, emergency brake assist, a lane departure warning system or lane assist system – in the view of accident researchers, such driver assistance systems undoubtedly and significantly increase the safety of commercial vehicles and help to protect anyone involved in road accidents. However, increasingly advanced safety technology concepts and driver assistance systems cannot hide the importance of one thing: The safety belt is still the most important measure for reducing the risk of serious injuries to vehicle occupants. This applies equally to all vehicle classes and thus, of course, to heavy-duty commercial vehicles too.

In recent years, the rate of seat belt use among truck drivers has certainly increased; but in Germany for example, figures from the Federal Highway Research Institute show that this rate (90 percent) is still below the rate for car occupants (98 percent). A survey conducted by DEKRA revealed a rate of just around 67 percent for occupants of commercial vehicles weighing over 12 metric tons in 2014. Accident researchers estimate that at least half of truck drivers who were not strapped in and suffered fatal injuries in a crash would have survived had they worn their seat belt. Accident research has also established that wearing a seat belt would lessen the severity of or even prevent injuries to commercial vehicle occupants in up to 80 percent of all serious accidents. Considering that the commercial vehicle itself is usually also the driver’s workplace, the issue of work safety is of crucial importance here.

As an in-vehicle restraining system, seat belts protect vehicle occupants from being flung around inside or even out of the vehicle. Because the seat belt is directly connected to the body of the vehicle, strapped-in occupants benefit fully from the effect of the crumple zone. The combination of the defined extensibility of the webbings with belt tensioner and belt force limiter means that the deceleration values for the occupants wearing a seat belt remain acceptable, even in serious collisions. Other passive safety components such as airbags are also designed for occupants wearing a seat belt and provide optimal protection only when the seat belt is worn.

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