Riding skill is an integer(from 0 to 8000). If the skill is less than 400, it is called [Unskilled]. If the skill is more than [Unskilled] and less than 2000, it is called [Beginner]. If the skill is more than [Beginner] and less than 5000, it is called [Skilled]. If a skill is more than [Skilled] and less than 8000, it is called [Expert]. If a skill is 8000, it is called [Master].
Riding skill is increased by 1 when you hit a monster whose level is more than (the skill -1000)/200 and you are riding. If (the skill -1000)/200 is less than your vehicle's level, the skill is increased additionally. The skill is also increased by 1 when you shoot and (the skill -1000)/200 is less than your vehicle's level and d2 is 1. The skill is also increased by 1 when you damaged and it is enough damage to cause unseating you.