In an expressway with 3 lanes in one direction, the center lane is primarily for which type of vehicles?

The correct answer highlights that the center lane of a 3-lane expressway is primarily designated for specific types of vehicles, particularly those that are capable of maintaining higher speeds and require more space for safety. Vehicles with cargo less than 1.5 tons, including cars and light trucks, are typically allowed in the center lane for efficient traffic flow.

In this context, the center lane usually facilitates smoother movement of vehicles that can travel at or near the speed of faster-moving traffic. It allows such vehicles to overtake slower ones in the other lanes while also providing an option for merging into faster-moving traffic.

The other choices, while they may involve scenarios where such vehicles might occasionally use the center lane, do not align with the primary purpose of that lane. Emergency vehicles may use any lane as needed to respond to emergencies, and bikes are generally not allowed on expressways due to safety concerns. Therefore, acknowledging the nature of expressway travel and vehicle classifications helps in understanding why light vehicles with cargo under 1.5 tons are appropriately placed in the center lane.