Audi News
An Analysis of Driver Assistance
By by: Alejandro Vukotich, Head of Assistance Systems, Markus Popken, Assistance Systems Application, Audi AG
Jun 29, 2005, 17:31

Our society's need for mobility and therefore the density of traffic is steadily rising. At the same time, we are seeing a sharp fall in the number of those seriously injured or killed by road traffic. These contrasting developments can be attributed to a large degree to progress in the domain of passive safety.

The overriding development objective until now has been to reduce the consequences of accidents. Examples of passive systems are the purely mechanical Audi ProconTen, which tensions the seat belt and pulls the steering column away from the potentially critical area of impact, airbags, pyrotechnic belt tensioners, and side impact protection.

Progress in the sphere of electronics has now paved the way for active systems that go even further. The aim is to prevent accidents from happening in the first place. Systems such as ABS and ESP improve the driver's control over the vehicle in critical driving situations where there would be a much higher accident risk without the assistance of these systems.

The introduction of new sensor technologies moreover makes it possible to implement active systems which – like human beings – are capable of registering the vehicle's surroundings and acting and implementing preventive measures based on this. Even if the perceptive capacities of such sensors is limited – again as is the case with humans – it is possible to create systems that assist the driver and thus provide appreciably greater convenience and safety.

Searching for accident causes: Audi Accident Research Unit

The accident research that Audi conducts provides the basis for deciding which systems provide significant customer benefit. In order to obtain detailed knowledge not simply of what happened in an accident but also of the background to individual accidents, various accidents are reconstructed and evaluated. Those involved in the accident are interviewed in depth, accident spots surveyed precisely, and police and medical accident reports appraised. One aim of the Audi Accident Research Unit is to gain an insight into the abstract notion of "human failure" and measure potential driver assistance functions in terms of actual accident scenarios. The question asked is: could the accident have been avoided with these functions? This makes it possible to make an initial prediction of the benefit of new assistance systems as early as the development phase.

The statistics reveal that "mental factors" are often the cause of accidents leading to fatalities. These include, for example, momentary drowsiness and basic inattentiveness, in this context defined as distractions to the driver while awake. Inattentiveness often results in unintentionally drifting out of the lane or overlooking other road users.
This can be identified by suitable systems and the system can alert the driver to their driving error.
Such systems consequently support the driver's skills without absolving them of responsibility, and therefore offer a substantial gain in convenience and safety.



Audi side assist with radar sensor

Audi side assist helps the driver to perform lane-changing manoeuvres. It provides a warning if the driver sets the turn indicator in preparation for changing lane but has overlooked another vehicle in the adjacent lane. This system alerts the driver to other vehicles cruising along in their blind spot, as well as to vehicles that are approaching rapidly.

The sensors comprise a 24 GHz radar system operating with two sensors in the rear bumper. The sensors have a range of about 50 metres to the rear. The areas in the blind spot alongside the vehicle are also covered. The radar sensor technology incorporates a high-performance computer unit that identifies objects from the raw targets picked up. This serves as the basis for alerting the driver accordingly.

The evaluation software has been developed entirely by Audi. It calculates when and how, i.e. in what way in which situation, the driver is alerted. It is the outcome of an evaluation of many field studies and psychological investigations.

The warning has to meet certain criteria. It must
• Allow the problem to be clearly identified. (What is the warning about?)
• Allow the system to be clearly identified. (Who is issuing the warning?)
• Be equally easy and clear to identify in all conditions.
• Attract attention appropriately. (The warning must not mask the problem)
• Not discredit the driver in the eyes of a fellow passenger. (Otherwise the system will not be accepted).



A purely visual warning display in the exterior mirror is the best way of satisfying these criteria. The pertinence of the image in the exterior mirrors is very high, as other road users can generally be seen in the mirror. In particular, such a display is less noticeable to the front passenger than an audible warning signal. For type approval reasons a warning display located outside the vehicle, for example on the exterior mirror, must not be visible to vehicles following on behind. This is achieved by means of the display's elaborate directional optics. It is designed in such a way that the display can virtually only be seen from possible driver positions.

To ensure that it is visible equally well in all conditions, the warning display has a brightness control based on ambient light conditions. The dynamic brightness characteristics must accommodate everything from a moonless night to bright midday sun in a hot climate.

For greater ease of distinguishing the display against a moving background, a flashing signal is used to provide the warning. Its periodic changing clearly distinguishes it from irregular background roar. The human eye is moreover highly sensitive to changes in contrast in the peripheral field of vision, in which the exterior mirror is positioned when the driver is looking in the direction of travel. It is much more probable that a flashing signal will be noticed than a continuous signal, because with every signal edge, a flash provides a change of contrast that can be detected.

In order not to distract the driver from the image in the mirror itself when looking directly at the mirror, a maximum flashing duration of less than one second was adopted. The signal's attention value scarcely rises even over lengthy flashing sequences.

In order to derive optimum benefit from a system, its limits need to be known. They can be learned faster if the assistance functions are still experienced even when a warning situation has not yet been reached. This is why Audi implemented the information mode for the Audi side assist, in addition to the warning mode. Irrespective of whether the turn indicator is set, all vehicles that could become critical if the driver decided to change lanes are displayed.

This information enables the driver to check at any time whether setting the turn indicator would prompt a warning, or they can check the system's assessment of the situation with just a glance. They can then compare the system's recommendations with their own opinion and thus rapidly come to understand the system.

The information display is emitted at a lower brightness level and is set such that the driver cannot see it out of the corner of their eye when looking straight ahead. In other words, the display is only subliminally within the peripheral field of vision. This avoids disturbing the driver as a result of frequent "flickering". Only when the driver looks directly into the mirror does the display become clearly visible.

The design of the displays necessitated extensive series of tests. Eye response with and without displays was recorded and evaluated using ultramodern eye tracking systems. Determining the characteristic maps for the subliminal information display and the clear warning display necessitated large-scale road tests with drivers of various builds because of their differing eye points, and of various ages on account of the fact that peripheral perception deteriorates with age.

The display brightness and warning moment can be set to personal preferences via the MMI menu. It will be possible to switch the entire system on and off in the Audi Q7 via a button near the driver's exterior mirror.



Audi lane assist

A further assistance function presented on the Audi allroad quattro concept is Audi lane assist. If the vehicle crosses the road markings without the driver setting the turn indicator, the steering wheel vibrates. The system is thus warning the driver that the car has been inadvertently allowed to drift out of its lane.

Here too, an intuitively understood form of warning has been chosen in the vibrating steering wheel. This feedback is known to the driver from the loud clattering sound heard when driving over corrugated road markings, and is also immediately understood by drivers who are unfamiliar with it, without it alarming the front passenger.

A video camera behind the windscreen acts as the sensor technology. An image processing function identifies the road markings and uses these to determine the vehicle's position within its lane. This means that both approach warnings – the system issues an alert as soon as the vehicle approaches the line – and crossing warnings – the system issues an alert when the vehicle is on or just over the line – are possible. The timing of this warning can be determined by the driver via the MMI, enabling them to adapt the desired system response to their personal driving style. The intensity of the vibration at the steering wheel can likewise be regulated by the driver, because haptic perception varies from one person to another. Audi lane assist can be switched on and off at any time via a button on the turn indicator lever.

Acceptance is the key to success

Whether or not future systems are actually realised depends not simply on their technical feasibility, but above all on the benefit to the driver. At Audi, the driver is at the centre not simply in terms of the physical configuration, but also for the development of future assistance systems.

Audi side assist and Audi lane assist have been defined and realised through constant fine-tuning with drivers. Behavioural studies and analyses of real accidents form the basis of an iterative process where the characteristics of the systems are continually cross-checked against the expectations of their users.


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