What is the maximum speed you are allowed to drive a truck with a permissible total mass of 4.0 t on autobahns?

For trucks with a permissible total mass of up to 3.5 tons, the general speed limit on autobahns is usually 100 km/h. However, once the permissible total mass exceeds 3.5 tons, such as your truck with 4.0 tons, a lower speed limit applies. According to German traffic rules, trucks over 3.5 tons are limited to a maximum speed of 80 km/h on autobahns to ensure safety due to their size and weight. This helps reduce stopping distances and the risk of accidents. So, driving at or below 80 km/h is mandatory for your vehicle type on highways.