## 4 Self-Organizing Maps Applied to Driving-Behavior Classification
### SOM-Based Drivers Grouping Regarding Fuel-Consumption
#### 4.3.1 SOM Classification Results
On the other hand, if we accumulate the percentages of medium, high, and very high consumption instants, we can observe that they practically match the Medium-High column of Table 3. This means that not only does this five-cluster classification provide comparable results, but it also allows one to thoroughly examine the detailed behavior formerly grouped as medium-high consumption DS. According to Figure 10, the Medium-High consumption cluster of Figure 9 can be detailed with the following groups:  
* Medium fuel consumption (yellow): corresponds to drivers who run the car at engine regimes similar to those achieved for the low consumption cars, but with the difference of a more extensive use of gas pedal, (i.e., medium PGP, low GP and medium ERPM). * High fuel consumption (green): corresponds to drivers who run the car at medium-high RPM, with moderate swiftness of the gas pedal operation (medium-high ERPM, medium-high PGP, and medium GP). * Very high fuel consumption (magenta): corresponds to drivers who are slightly more aggressive that those from the preceding group (high ERPM, high PGP, and medium-high GP). Additionally, with this new cluster distribution, more actions can be indicated to drivers to modify their DS. Thus, in contrast with Table 5, where Medium (yellow) to Very high (magenta) consumption classes were aggregated, in Table 8, actions were added for each individual newly identified cluster. In contrast, actions for Very low and Low consumption groups remain unchanged. The action Lower RPM/Keep gas steady was transformed into the sequence Lower RPM/Operate gas softly \(\rightarrow\) Lower PGP/Lower RPM \(\rightarrow\) Lower PGP/Keep gas steady, as can be noticed when comparing Table 5 with Table 8. This happens because, differing from the uniform DS of the big Medium-High consumption group of the three-cluster classification (green group in Figure 9), the Very high (magenta) fuel-consumers are required to lower both RPM and PGP, because they drive at high RPM. In contrast, High (green) consumers run engines at moderated RPM rates. However, the latter swiftly operate the gas pedal at moderately high percentages, consequently being required to use it less and more smoothly. Finally, Medium (yellow) consumers operate the gas pedal smoothly but their usage percentage is still high, so they are required to further reduce gas pedal usage. Should drivers follow the recommendations that are displayed in Table 8, a noticeable reduction in fuel consumption is expected to occur. However, because the level of engagement of motorists with the provided advice may vary depending on behavioral characteristics of each individual, the expected improvement on fuel economy must be cautiously analyzed. For that reason, Table 9 was elaborated to estimate the expected improvement when considering a minimal level of engagement with the system that would allow drivers to modify their DS to the immediately adjacent cluster. \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 (yellow) & Lower RPM/Operate gas softly \\ High (green) & Lower PGP/Lower RPM \\ Very high (magenta) & Lower PGP/Keep gas steady \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Actions associated to the five-cluster classification. As can be seen in Table 9, obtained from the values displayed in Table 6, if drivers could only improve their DS to the best adjacent class, reductions in fuel consumption ranging from 9.54% up 31.5% are expected, with even higher performances for strongly-engaged drivers, showing that a significant reduction in polluting agents could be expected if this system was implemented in cars. This potential reduction is significantly greater than the already existing systems, which were exposed in Section 1.2, making this approach a promising solution.