# Drivers' Psychomotor Reaction Times Tested with a Test Station Method
## 3 Results and Discussion  
The statistical material presented below was obtained by the authors of the paper as part of students' theses and research projects. The paper presents the results obtained on the  
Figure 4: Result of a single driver’s test, including the distribution of intervals between the stimuli and errors marked. basis of about few thousand tests carried out on a group of 82 respondents aged between 21-24 years old and having a driving license. The results were processed statistically. In the case of each analyzed maneuver (turning, braking and combined braking and turning) the results were presented in the form of histograms, showing a relative frequency as a function of the reaction time and graphs presenting the total relative frequency as a function of the reaction time. Additionally, the mean values and medians of the reaction times were determined. The method of processing the results is presented on the example of reaction times obtained for turning. The histogram (Figure 5) shows the number of responses in a reference time interval. Based on the same data an analysis of probability density distribution was performed (Figure 6). An analysis of the histogram presented above suggests that distribution of the results does not correspond to a standard normal distribution. A clear limit of the minimum reaction time can be observed, which in this case amounted to 0.38 s. The upper limit has not been identified. The results included ones which exceeded a few seconds, but they were considered as grave errors and eliminated from further analysis. The most numerous group of responses ranged from 0.6 to 0.7 s. The mean value for the analyzed test results was 0.81 s, while the median amounted to 0.75 s. Taking into account the distribution function of the reaction time distribution at turning it can be demonstrated that 85% \(\div\) 95% of the studied population's reaction times ranged from 1.0 to 1.4 s (Figure 6). Another examined behavior of the driver was panic braking, which involved the instant shifting of the leg from the accelerator to the brake and pushing the brake strongly. Such a maneuver is far more complex than fairly simple turning, which extends the total  
Figure 5: Histogram presenting the number of responses at turning. Figure 6: Distribution function of the reaction time distribution at turning. reaction time to a stimulus. It can be observed in histogram (Figure 7), where the most numerous group of responses fell within the range between 0.9 and 1.0 s.  
The minimum observed reaction time was 0.49 s, while only one response fell within the range of 0.4 \(\div\) 0.5 s. Another range with a low number of responses was 0.5 \(\div\) 0.6 s, with only four responses. The distribution function of the reaction times at braking shows that 85% \(\div\) 95% of the studied population's responses ranged between 1.3 and 1.6 s (Figure 8). Braking with simultaneous turning of the steering wheel was the most complex maneuver. Despite certain independence of the muscular reaction at turning and braking it turns out that the drivers needed most time to make such maneuvers. According to the histogram (Figure 9) the minimum reaction times observed for such a complex maneuver ranged from 0.6 to 0.7 s. The most numerous group of answers ranged from 1.1 to 1.2 s, while the 85% \(\div\) 95% quantiles amounted to 1.5 \(\div\) 1.7 s, respectively (Figure 10). Figure 8: Distribution function of reaction time distribution at braking. Figure 7: Histogram presenting the number of responses to a braking signal. The obtained characteristic results of analyses from all tests are presented in Table 1.  
The obtained average values (median) of reaction time are consistent with those presented by the authors in Ref. [8], who analyzed the behavior of drivers in real road conditions. However, their research shows that the reaction time in the case of a turning maneuver is about 0.3 s longer than in the case of a braking maneuver.