## 4 Self-Organizing Maps Applied to Driving-Behavior Classification
### SOM-Based Drivers Grouping Regarding Fuel-Consumption
#### 4.3.1 SOM Classification Results
Figure 10 and Table 6 show the five-cluster grouping obtained after this re-computation and the associated fuel consumption for each cluster, respectively. Nevertheless, despite the existence of a higher number of groups, the relationships identified in Figure 9 remain. Thus, the blue and red clusters (Low and Very low consumption) are kept barely unaltered both in position and number of elements. In contrast, three new classes appear from the former Medium-High consumption group, namely Medium, High, and Very High (yellow, green, and magenta, respectively). \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Cluster Label** & **Average Value** & **Variance** & **Maximum Value** \\ \hline Very low (red) & 2.75 & 1.04 & 6.66 \\ Low (blue) & 3.04 & 1.54 & 7.80 \\ Medium (yellow) & 4.44 & 2.21 & 10.1 \\ High (green) & 5.42 & 3.13 & 11.4 \\ Very high (magenta) & 7.81 & 5.38 & 12.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Fuel consumption (L/100 km) parameters of the five-cluster classification. \begin{table}
\begin{tabular}{l c} \hline \hline
**Current Cluster** & **Required Action** \\ \hline Very low (red) & Keep driving style \\ Low (blue) & Lower RPM/Switch to a higher gear \\ Medium-High (green) & Lower RPM/Keep gas steady/Lower PGP \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Actions that are associated to the three-cluster classification. Being the aforementioned partitions, extracted from Figure 10, jointly analyzed with the statistical data contained in Table 7, we can assert that this SOM-based grouping is finer, and more meaningful information can be extracted when compared to the three-cluster classification. \begin{table}
\begin{tabular}{l c c c c c} \hline
**Driver** & **Very Low (\%)** & **Low (\%)** & **Medium (\%)** & **High (\%)** & **Very High (\%)** \\ \hline D1 & 4.7 & 20.0 & **44.7** & **30.6** & 0 \\ D2 & 48.3 & 10.3 & 2.3 & 32.2 & 6.9 \\ D3 & 21.8 & 33.3 & 13.8 & 30.0 & 1.1 \\ D4 & 7.8 & 51.1 & 22.2 & 18.9 & 0 \\ D5 & 33.3 & 26.5 & 10.3 & 25.3 & 4.6 \\ D6 & **71.9** & 10.4 & 9.4 & 8.3 & 0 \\ D7 & 14.0 & 33.7 & 18.6 & 29.1 & 4.6 \\ D8 & 14.9 & 29.7 & 8.1 & 37.8 & 9.5 \\ D9 & 8.1 & 38.4 & 31.4 & 22.1 & 0 \\ D10 & 56.3 & 0 & 16.1 & 25.3 & 2.3 \\ D11 & **78.6** & 11.9 & 1.2 & 8.3 & 0 \\ D12 & 10.6 & 33.0 & 37.2 & 19.2 & 0 \\ D13 & 14.0 & 46.5 & 15.1 & 24.4 & 0 \\ D14 & 8.4 & 25.3 & **31.3** & **35.0** & 0 \\ D15 & 2.5 & 45.7 & 24.7 & 23.4 & 3.7 \\ D16 & 13.1 & 40.5 & 30.9 & 15.5 & 0 \\ D17 & 38.1 & 21.4 & 10.7 & 21.5 & 8.3 \\ D18 & 2.7 & 48.0 & 19.2 & 26.0 & 4.1 \\ D19 & 15.6 & 30.00 & 21.1 & 32.2 & 1.1 \\ D20 & 32.2 & 26.9 & 22.6 & 18.3 & 0 \\ \hline \end{tabular}
\end{table} 
Table 7: Percentage of the route that each driver travels using different fuel-consumption DS (five-cluster classification). Figure 10: Three-dimensional views of the five-cluster fuel consumption classification results. The clusters were labeled as Very low (red), Low (blue), Medium (yellow), High (green), and Very high (magenta). (**a**) Displays the cluster distribution considering PGP, ERPM and GP. (**b**) Considers PGP, ERPM and XACC var. (**c**) Displays clusters regarding PGP, GP and XACC var, and (**d**) considers ERPM, GP and XACC var. The fuel-consumption-associated DS ratios for each driver are recalculated in Table 7 in order to verify that the five-cluster classification adds information to the already existing groupings, mainly with the purpose of personalizing the assessment of the most aggressive drivers. In this case, D1, D6, D11, and D14 are analyzed again to inspect whether the new cluster classification changes the information contained in Table 3. For these drivers, the percentages of Very low and Low consumption remain practically unchanged with respect to the three-cluster table.