## 3 Results and Discussion
### Effect of IC Design
#### 3.4.1 Reaction Time  
The resulting RTs for each of the ICs are given in Tables 1 and 2 (Appendix 1). The Kolmogorov-Smirnov test (significance level \(\alpha=0.05\)) showed that values of RT as well as \(\ln(RT)\), both averaged between the participants and between the ICs, had normal distribution. This corresponds to the typical distribution of human reaction time [4].  
Table 3 shows a summary of the results. To assess the effects of IC designs on RTs, the results were evaluated for each pair of ICs using the paired \(t\)-test. The significance level was \(\alpha=0.05\).  
The shortest mean RTs were achieved on IC04 and IC06, compared to other ICs (\(t\)-test resulted in \(p<0.05\), except between IC06 and IC03 where \(p=0.1\) in the first session, and between IC04 and IC07 where \(p=0.16\) in the second session). The shortest individual time (451 ms) was achieved in the second session by a 48-year-old woman (participant no. 18) on IC06, with a correct reading. The difference in RT between IC04 (analog speedometer) and IC06 (digital speedometer) was not statistically significant. A common feature of IC04  
Figure 6: Relationship between RT and reading error (**a**), and between RT and relative reading error (**b**).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Session 1** & **IC** & **01** & **02** & **03** & **04** & **05** & **06** & **07** \\ \hline \multicolumn{6}{c}{\(v_{s}\), km/h} & 55 & 47 & 52 & 58 & 54 & 40 & 46 \\ RT mean & 2723 & 3180 & 2383 & 1843 & 2756 & 1889 & 3234 \\ RT SD & 1175 & 1532 & 877 & 712 & 1843 & 2193 & 2890 \\ RT median & 2408 & 2642 & 2202 & 1773 & 2267 & 965 & 1633 \\ RT min & 1149 & 1350 & 1171 & 829 & 560 & 473 & 872 \\ RT max & 6012 & 7671 & 5858 & 4464 & 8503 & 10,233 & 11,116 \\ RT range & 4863 & 6321 & 4687 & 3635 & 7943 & 9760 & 10,244 \\ \hline
**Session 2** & **IC** & **01** & **02** & **03** & **04** & **05** & **06** & **07** \\ \hline \multicolumn{6}{c}{\(v_{s}\), km/h} & 121 & 85 & 159 & 162 & 93 & 82 & 104 \\ RT mean & 2865 & 2786 & 3118 & 1824 & 2927 & 1057 & 2343 \\ RT SD & 1454 & 1296 & 1566 & 904 & 2492 & 515 & 1942 \\ RT median & 2584 & 2337 & 2574 & 1521 & 2151 & 879.5 & 1438 \\ RT min & 1028 & 1387 & 1303 & 896 & 69 and IC06, compared to other ICs, is that the speedometer is positioned centrally, which is distinctive of the IC. The left or right position of the speedometer, such as on IC01, IC02, and IC03, was not identified as a factor that affects RT.  
Like the IC06, the IC05 and IC07 also have digital speedometers positioned in the center of the IC. However, the mean RTs were significantly longer than those in IC04 and IC06. The reason may be the presence of round instruments that resemble a speedometer and increase the time needed to find the speedometer. The longest time (11,116 ms) was recorded by a 52-year-old woman (participant no. 21) in the first session on IC07, with a correct reading.  
None of the ICs from the sample was statistically confirmed as the IC with the longest mean RT.  
In addition to the duration of the saccade and fixation, the accuracy of the reading is also affected by the visual characteristics of the speedometer, the analysis of which is given in the next section.