Answer
The age distribution of cars on 1 January 2020 can be found in Figure 2. It shows that it takes an average of ten years before at least half the car fleet is equipped with a new or renewed safety feature. On the reference date of 1 January 2020, for example, at least 36% of cars were equipped with electronic stability control, which had become mandatory in 2014.
Figure 2. Age distribution of Dutch cars on 1 January 2020. At this point in time, the total number of Dutch cars amounted to 8,677,911. Source: Statistics Netherlands/Netherlands Vehicle Authority [36].