## 4 Case Study
### Detecting Failure Modes for IVIS  
The primary user interface of the original IVIS is depicted in Figure 2. From this IVIS, many tasks can be executed. In this study, we focused on the commonly used tasks that concerned navigation, climate, media, telephone, and radio. The results of the HTA for these tasks are described in a tabular list, as shown in Table 6. The experimenters observed the processes of the users completing the tasks. After that, SHERPA was employed to identify the failure modes related to UX. A total of 25 failure modes were identified, as listed in Table 7. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Code** & **Task** & **Rule** \\ \hline
0 & Performing relevant tasks & Plan 0: do any of 1, 2, 3, 4, or 5 in any order \\
1 & _Media_ & Plan 1: do 1.1, 1.2, 1.3, 1.4, and 1.5 in order \\
1.1 & Play media & Plan 1.1: do 1.1.1, 1.1.2, and 1.1.3 in order \\
1.1.1 & Click on MENU & \\
1.1.2 & Click on Media & \\
1.1.3 & Click on Play & \\
1.2 & Adjust volume & Plan 1.2: do 1.2.1, 1.2.2 in order \\
1.2.1 & Click on blank area & \\
1.2.2 & Slide volume bar & \\
1.3 & Switch music & Plan 1.3: do 1.3.1, then do 1.3.2, 1.3.3, 1.3.4, and 1.3.5 in any order \\
1.3.1 & Click on Selection & Plan 1.3.1: do 1.3.1.1 and 1.3.1.2 in order \\
1.3.1.1 & Enter playlist & \\
1.3.2 & Click on Previous & \\
1.3.3 & Click on Next & \\
1.3.4 & Click on Repeat & \\
1.3.5 & Click on Shuffle & \\
1.4 & Adjust process & Plan 1.4: do 1.4.1 and 1.4.2 in any order \\
1.4.1 & Slide to right & \\
1.4.2 & Slide to left & \\
1.5 & Close media & Plan 1.5: do 1.5.1 and 1.5.2 in order \\
1.5.1 & Click on Stop & \\
1.5.2 & Click on MENU & \\
2 & _Navigation_ & Plan 2: do 2.1, 2.2, 2.3, and 2.4 in order \\
2.1 & Open navigation & Plan 2.1: do 2.1.1 and 2.1.2 in order \\ \hline \hline \end{tabular}
\end{table} 
Table 6: HTA for the original IVIS regarding media, navigation, telephone, radio, and climate. Figure 2: Primary user interface of the original IVIS. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Code** & **Task** & **Rule** \\ \hline
2.1.1 & Click on MENU \\
2.1.2 & Click on Navigation \\
2.2 & Choose place \\
2.2.1 & Set route \\
2.2.2 & Set destination \\
2.2.2.1 & Save current position \\
2.2.2.2 & Historical records \\
2.2.2.3 & Home address \\
2.3 & Start navigating \\
2.3.1 & Click on Selection \\
2.3.2 & Select route \\
2.3.3 & Click on Start \\
2.4 & Close navigation \\
3 & _Telphone_ \\
3.1 & Open phone options \\
3.1 & Click on MENU \\
3.1.2 & Click on Call \\
3.2 & Select contacts \\
3.2.1 & Dial number \\
3.2.2 & Contacts \\
3.2.3 & Recent \\
3.3 & Make calls \\
3.3.1 & Click on dial button \\
3.3.2 & Click on hang-up button \\
3.4 & Return Home \\
4 & _Radio_ \\
4.1 & Turn on the radio \\
4.1.1 & Click on MEUN \\
4.1.2 & Click on radio options \\
4.2 & Switch radio \\
4.2 & Click on bands \\
4.2.1 & Select AM \\
4.2.1.2 & Select FM \\
4.2.2 & Click on the radio list \\
4.2.3 & Click on manual \\
4.3 & Add station \\
4.3.1 & Long press station \\
4.3.2 & Click on blank to add box \\
4.4 & Return home \\
5 & _Climate_ \\
5.1 & Turn on the air conditioner \\
5.1.1 & Click on MENU \\
5.1.2 & Click on vehicle button \\
5.1.3 & Click on blank \\
5.1.4 & Click on air conditioner button \\
5.2 & Set air conditioner \\
5.2.1 & Regulate air volume \\
5.2.1.1 & Increase air volume \\
5.2.1.2 & Decrease air volume \\
5.2.2 & Regulate temperature \\
5.2.2.1 & Turn down the temperature \\
5.2.2.2 & Turn up the temperature \\
5.2.3 & Regulate blowing mode \\
5.3 & Return home \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._