# AI-Driven Predictive Maintenance for Workforce and Service Optimization in the Automotive Sector
## 3 Preliminaries
### Data Analysis
#### 3.3.2 Exploratory Data Analysis  
This section examines the features in the dataset and the dependent changes of these features. Figure 4 visualizes the total number of maintenance service records by year. While the number of services increased gradually until 2019, the number of visits started to decrease in 2019 and beyond. The COVID-19 pandemic, which started in 2019, had an impact on this decrease. Vehicle owners who do not leave their homes and do not use their vehicles may not need to have their vehicles serviced. Figure 5 examines the time between the vehicles visiting for maintenance. The median value is 382 days, and customers' visit habits vary considerably. In addition, different Maintenance Periods can be assumed for other vehicles. Hence, the time between two treatments can vary greatly depending on the car brand or type. To elaborate on the variability mentioned in Figure 5, we present a comparison of Days Between Service Visits for two anonymized brands (Brand A and Brand B). As shown in Figure 6, Brand A vehicles exhibit a shorter median service interval (\(\sim\)210 days), while Brand B vehicles tend to have longer intervals (\(\sim\)380 days) between maintenance visits. This variation may be attributed to differences in usage patterns. Brand A is commonly used for commercial or fleet operations, leading to higher mileage and more frequent maintenance needs. In contrast, Brand B includes more private or premium-use vehicles, which are serviced less frequently. This insight supports our assertion regarding the effect of vehicle type and usage context on service behavior. Figure 4: Annual total maintenance service visits. Figure 5: Box plot of days between service visits. Figure 6: Comparison of maintenance frequency between Brand A and Brand B vehicles. Figure 7 analyzes the number of maintenance visits according to vehicle age. It has been observed that the number of maintenance visits decreases as the age of the vehicle increases. There are two main reasons for the decline here: the 2-year warranty period and the economic advantage of special services. The decrease in the number of services starts from the age of 2 years. Vehicles are under warranty for two years from the date of purchase. Owners continue to take their vehicles to authorized service centers so that the vehicle's warranty is not impaired. After the vehicle turns two years old, the habit of bringing it to authorized services may decrease. Another reason for this decline is the customers' deviation from authorized service providers to secondary, non-authorized repair stations due to their lower maintenance service prices. The distribution of time between maintenance visits of male and female customer vehicles is visualized in Figure 8. According to this visual analysis, after the number of days between two maintenance exceeds 400, regardless of gender, the number of maintenance service records decreases. In addition to the visual analysis in Figure 8, we calculated descriptive statistics for the Days Between Service Visits across genders. For male customers, the average interval was approximately 340 days with a standard deviation of 185 days, while female customers  
Figure 8: Distribution of vehicle visits for male and female customers. Figure 7: Number of maintenance visits by vehicle age. exhibited a slightly higher average of 370 days, with a standard deviation of 205 days. These values align with the visual trends, where male customer vehicles display a sharper peak around the 300-350 day range, suggesting more frequent and routine maintenance behavior. In contrast, female customer vehicles demonstrate a broader spread, indicating a tendency toward longer intervals between service visits. The overall dataset shows a mean of 353.2 days, median of 350 days, and standard deviation of 195.1 days, confirming that most vehicles are serviced annually, with some variability across customer segments. In Figure 9, the distribution of the measured kilometers of the vehicles during the service visits is examined.