In Street you can have one adult passenger as long as they have proper restraints. Young children can ride in addition as long as they are in car seats or seat belts (as appropriate by size). You cannot hold children on your lap during a race, this is non-negotiable. The safety committee must approve the restraints and the number of passengers in your vehicle. No animals in the vehicle.
In Pro Street you can have one passenger as long as they have proper restraints and a good fitting helmet. No animals in the vehicle.
In Competition there are no passengers allowed in the Cheater classes. In studs and bare rubber you may have one passenger as they have proper restraints and a good fitting helmet.