# Assessing Drivers' Physiological Responses Using Consumer Grade Devices
## 2 Materials and Methods
### User Study
#### 2.5.2 Tasks  
This study had a within-subject design. It consisted of three phases: Baseline, easy driving, and demanding driving. The duration of each phase was 6-8 min to ensure at least a 5-min-long window  
Figure 5: Positioning of Empatica E4 and Bittium Faros 360. E4 should be placed on the wrist of a non-dominant hand in a way that electrodes are on the line that goes between middle and ring finger. Faros with the textile belt should be placed right below the chest muscle [80].  
of data, as recommended for short-term recordings of physiological signals by the European Society of Cardiology [79; 82].  
Phase 1: Baseline  
Physiological signals such as HR and HRV differ among people therefore, we first had to collect baseline data for each participant. Since there is not a standardized procedure for baseline measurements, we followed the recommendations by [PERSON] et al. [79]. To create similar environment with the following driving tasks, the baseline measurements were also collected in a sitting position. The test drivers were told to sit in a chair with their legs straight (not crossed), keeping their knee angles at 90 degrees. They were asked to try to relax and stay calm, to lean their head back, keep their eyes closed, and to ensure normal blood flow to the wrists, place their arms on the supporters with hands facing up (Figure 6a).  
The 5-min measurement began with a short beep from Faros that indicated a successful initialization of measurement system. During this period, all light and noise sources were turned off and remained off until the end of the study process in order to reduce potential distractions that could affect the measurement process.  
Phase 2: Easy Driving  
Phase 2 and 3 were performed in a driving simulator. The participants' task was safe driving in a very simple driving scenario (Figure 6b). The participants were asked to drive on a two-way one-lane six-kilometer country road with no other vehicles or pedestrians. The speed limit was 90 km/h, and participants were not asked to follow any pre-defined path.  
Phase 3: Demanding Driving  
In the third phase, the participants' primary task remained safe driving. However, in this task the participants had to follow a specific route communicated with a navigation system displayed on a built-in head-up display. In this phase, the driving scenario was much more demanding as it featured  
Figure 6: Driver’s position during three phases of measurement: (**a**) Baseline, (**b**) easy driving, (**c**) demanding driving [80].  
six kilometers of two-lane highway and two kilometers of city road with a lot of vehicles, intersections and pedestrians.  
While on the highway (Figure 6c), the participants faced many critical situations, including a truck driving in the opposite direction, work on the road, unsafe overtaking by another vehicle, and traffic accident while driving in fog. The driver experienced critical situations also on the city road such as pedestrians crossing the road outside crosswalks, a bike forcing the driver's right of way, a child on the road running after a ball, etc.