A car covers $AB$ distance with first one-third at velocity $v_{1}$ m s$^{-1}$, second one-third at $v_{2}$ m s$^{-1}$ and last one-third at $v_{3}$ m s$^{-1}$. If $v_{3} = 3v_{1}$, $v_{2} = 2v_{1}$ and $v_{1} = 11$ m s$^{-1}$, then the average velocity of the car is \_\_\_\_ m s$^{-1}$.