Final answer:
Motorcycle riders are allowed to use carpool lanes, which is typically allowed irrespective of the number of passengers, but local laws and regulations should be checked.
Step-by-step explanation:
Motorcycle riders are typically allowed to use carpool lanes, also known as High Occupancy Vehicle (HOV) lanes, regardless of the number of passengers they have. The specific rules can vary by location, but generally, motorcycles are considered inherently high occupancy vehicles due to their design for individual transport and their ability to reduce congestion and improve air quality. This is in contrast to cars, which require a certain number of passengers to legally use carpool lanes. It is always important for riders to check local laws and regulations to understand when they are permitted to use these lanes.