Which type of container must not exceed 200 gallons in capacity when used on passenger-carrying vehicles?

The answer is LP-gas containers, primarily because regulations and safety standards are established to limit the capacity of propane storage on passenger-carrying vehicles to enhance safety. LP-gas containers designed for use in vehicles must adhere to strict guidelines, one of which includes a maximum capacity of 200 gallons. This limit is in place to minimize the risks associated with transporting large quantities of propane, such as potential leaks, explosion hazards, and the challenges of managing a fuel emergency.

In contrast, aqueous containers, fuel oil tanks, and compressed gas cylinders might have different regulations and safety considerations, but they do not fall under the specific guidelines pertaining to LP-gas on passenger-carrying vehicles. Therefore, adhering to these standards is crucial for safe transportation and compliance with safety regulations.