Table 1 shows the breakout of allotted vacation hours by the number of drivers. You can see that the 5 most senior drivers (whom each get 6 weeks off) account for almost 15% of all the allotted vacation hours. By comparison, my classmates (4 drivers) account for .08%. The average driver will get 80 hours of vacation in 2020.
Creating groups makes it easier to visualize the fact that 30% of the drivers do not have much vacation.
Using seniority as the primary means of bestowing benefits tilts the scale in ways new drivers feel but often lack the words to express. It works against newbies. New drivers are doing extra work to cover for everyone else's vacation. The current policy forces them to wait to years to receive one week of vacation.
Figuring out an equitable vacation policy would reduce the high initiation burden that new drivers face. Addressing such issues would aid in the retention of drivers.
Here is the link to the data.