Driving pleasure scientifically measured for the first time

Muamer Hodzic September 6, 2007

Scientists have scientifically analysed the driving pleasure experienced by motorists for the first time. Experts from the Fraunhofer Institute in Rostock, Munich Technical University and Mercedes Customer Research collaborated in the unique pilot study which involved testing various methods for measuring drivers’ emotions. They were able to ascertain what drivers feel and which aspects affect driving pleasure by means of voice analysis, facial-expression recognition and psychological questioning.

In order to measure and evaluate the drivers’ emotional reactions, Mercedes-Benz used two models featuring different equipment and appointments for the field tests: the new C-Class and the Mercedes-Benz 190 E from 1983. Eight drivers aged between 33 and 53, a mix of men and women, drove the two saloons at a proving ground and negotiated different types of route including country roads, motorway stretches and a winding handling course. A data recorder also logged details such as road speed, longitudinal acceleration and lateral acceleration as well as the cars’ precise positioning data.

Two modern emotions-research methods proved extremely practical for measuring driving pleasure: facial-expression recognition and voice analysis.

Facial expression has been an undisputed indicator of emotions ever since the American psychologist Paul Ekman completed major studies in this field. Now aged 73, Ekman discovered that 43 facial muscles react sensitively to each excitation, and that these unconscious movements always follow the same pattern. Based on these findings, scientists at Munich Technical University developed a process for interpreting facial expression by computer, thus making it possible to observe emotions over a longer period and in different situations, including when driving a car.

Facial-expression recognition in a car: 140 facial features observed

In the driving pleasure study carried out by Mercedes-Benz, cameras inside the car recorded the drivers’ facial expressions. When the pictures were subsequently analysed in the laboratory, 60,000 individual images were copied from the video recordings and then evaluated by computer for facial-expression recognition. A total of around one million images were analysed in this way.

To detect the muscle movements, the computer measures 140 features on each face, enabling it to “see” laughing, for example, during which the corners of the mouth move towards the ears. In addition, the computer program also records the intensity of the expressions, allowing the scientists to differentiate between the degrees of typical emotions such as anger, sorrow, disgust, fear, enjoyment and surprise. Enjoyment readings which were above individually defined thresholds were interpreted as driving pleasure.
The drivers had a joyful smile on their faces more often and for longer when driving the new C-Class as opposed to the Mercedes-Benz 190 E. The difference in this “driving pleasure factor” varied by up to 48 percent from person to person. It all depends on the type of driver though, since the more experienced motorists also enjoyed driving the older car. For example, they smiled when the rear end drifted slightly on the tight bends of the handling course. But other drivers were not so confident in such situations and experienced more driving pleasure in the C-Class with ESP®. By way of example, one lady behind the wheel of the new Mercedes model posted a score of 4.3 for driving pleasure, while the figure measured when she drove the 190 E model was just 2.9.

Voice analysis: interpreting emotions through tones and frequencies

Another method of testing and measuring emotions objectively is by speech analysis: the tone of voice changes depending on the person’s frame of mind.

Scientists from the Fraunhofer Institute in Rostock have developed computer-based methods designed to recognise the most subtle of changes in a person’s tone of voice. To do this, they split the voice into different frequency bands, monitor how the person speaks and can then conclude whether the person feels positive or negative emotions in a given situation. The experts were in phone contact with the test participants and encouraged them to describe their impressions. This “thinking aloud”, a tried-and-trusted method of psychology, made the emotional condition of the drivers audible and gave the researchers enough data material for computer-based voice analysis in which 1200 features were analysed in each case.

Analysis of the sound recordings went on over a period of around four weeks, during which the Fraunhofer experts were able to ascertain how often and on which route sections the drivers were in a positive frame of mind, using this as their basis for interpreting the level of driving pleasure. Looking at the results of the voice analysis for all route sections as a whole, it can be seen that the drivers of the C-Class were in a positive frame of mind – i.e. experiencing driving pleasure – on 72 percent of the route sections. When driving the Mercedes-Benz 190, meanwhile, the participants were in a positive frame of mind on 36 percent of the route sections.

Psychological questioning: safety a vital factor for driving pleasure

The driving pleasure measurements obtained by means of facial-expression recognition and voice analysis were accompanied by psychological questioning before and after each drive. For the experts from Mercedes Customer Research, the aim of this exercise was to find out what the drivers believed contributed to the level of driving pleasure. The statements made by the test participants were clearly dominated by aspects such as vehicle control and safety – areas in which the C-Class outshines the Mercedes-Benz 190 E.

The pilot study showed that driving pleasure can be measured using modern emotions-research methods and, therefore, can become a verifiable criterion for evaluating cars in future. Mercedes-Benz will continue its work in this field and integrate driving pleasure measurements into other scientific field tests involving drivers. In this way model development work is to attach even greater importance to driving pleasure – alongside safety, comfort and other measurable criteria. In future, the sum of all a car’s characteristics will culminate in a key concept: refinement. This describes the classic Mercedes way of driving, where agility and dynamism make for enjoyment whilst, at the same time, safety and comfort make for well-being. A Mercedes-Benz ticks both boxes – depending on the driving situation and what the driver wants.