What is the maximum speed limit for a large size truck on national expressways?

The correct answer of 80 km/h reflects the regulations set by Japanese traffic laws for large size trucks operating on national expressways. This speed limit is specifically designed to enhance safety on the roads, as larger vehicles such as trucks have longer stopping distances and can pose more significant risks to other road users if traveling at higher speeds.

Conversely, options like 100 km/h or 120 km/h exceed the speed limit appropriate for large trucks, as those speeds are typically designated for passenger vehicles. Allowing larger vehicles to travel at these higher speeds would likely result in increased danger, particularly in adverse weather conditions or in heavy traffic, thus the law prioritizes a more sustainable and safer approach when it comes to managing large trucks on expressways. The choice of 60 km/h is also inaccurate as it is too low for expressway travel, which is intended to facilitate faster movement of vehicles while still adhering to safety protocols.