Motorcycles are vehicles commonly driven by the people of Earth.
A motorcycle is first seen in Dragon Ball being used by Bulma, who drives Goku and herself around on it whilst searching for the Dragon Balls. Bulma owns at least three motorcycles: a white motorcycle Goku borrowed to save her from a pterodactyl, a red one she used to go on the see with Goku and the Turtle, and a yellow motorcycle she used to go at Aru Village. Launch is seen riding a one wheeled motorcycle on occasion, during her days as a bandit.
Dr. Flappe owns a snowmobile, Ninja Murasaki stole it when he thought he had the Dragon Balls, instead being Goku's lunch. In the video game Dragon Ball: Origins 2, the soldiers near Muscle Tower also use snowmobiles, and in Dragon Ball Z: Attack of the Saiyans the first floor of the Muscle Tower is a garage full of snowmobiles.
The policeman in West City who helped Goku find Bulma's house uses an airbike that he got fixed by Dr. Brief. A motorcycle policewoman modeled after and voiced by the Olympic gold-medalist Kaori Matsumoto appears in the movie Dragon Ball Z: Battle of Gods, during Bulma's birthday party, observing the battle against the God of Destruction Beerus from afar.
World Tournament Announcer uses a capsule airbike during the 22nd World Martial Arts Tournament to follow Tien Shinhan and Goku at the end of their battle in the tournament. The announcer's airbike is also an item in Dragon Ball RPG: Shōnen-hen.
Goku is often shown on a bike on the covers of Dragon Ball manga chapters. In the PSP game Dragon Ball Z: Shin Budokai, which takes place in Age 776, two years after the defeat of Kid Buu, Yamcha mentions that Goku recently got a bike. Goku says that the bike is broken right now and Gohan mentions that no matter how many times his father tries to fix it, it falls apart again. Yamcha then suggests he should talk to Bulma about it.
In Dragon Ball GT, Goku, Pan and Trunks uses space scooters to go into a ship about to fall into a sun, and searches it for a Black Star Dragon Ball. With less than a minute until the ship is destroyed, the gang rushes and gets on their scooters after finding the Dragon Ball and rescuing a green boy. They get off the ship before it melts in the sun, but when their scooters get caught up in the gravity pull, they abandon them while Giru launches a grappling hook at their ship.