At 16 you can ride a moped, with a maximum speed of up to 45 km/h.
At 17 you can ride a motor cycle with an engine size of up to 125cc. (There are other restrictions, on power in kilowatts and on power–to–weight ratio.)
At 19 there is no restriction on engine size, and the other restrictions (on power and power–to–weight ratio) are relaxed somewhat.
At 21 you can ride any motor cycle.
© Haydn Thompson 2017