Which condition allows passengers to stand while a vehicle is in motion?

The condition that allows passengers to stand while a vehicle is in motion is when it is permitted by the vehicle's transportation license. This regulation is specifically designed to ensure safety and compliance with local transportation laws. A bus may have specific stipulations outlined in its license that dictate how it can operate, including whether standing passengers are allowed.

Licensing authorities assess factors such as vehicle type, safety features, and intended use when issuing transportation licenses. In many cases, commercial vehicles like buses are required to have seats for all passengers to enhance safety during transit. However, if the license specifically allows for standing passengers under certain conditions, then those conditions must be followed.

The other options do not constitute valid reasons because full capacity does not inherently mean standing is safe or permitted, the condition of the road does not influence the legality of standing, and age alone does not determine whether a passenger can safely stand in a moving vehicle.