What is the maximum speed you are allowed to drive a truck with a permissible total mass of 40 t on autobahns?

In Germany, trucks with a permissible total mass over 3.5 tons have a maximum speed limit of 80 km/h on autobahns unless a lower speed is indicated by traffic signs. This rule ensures safety because heavier vehicles require longer stopping distances and have different handling characteristics at high speeds. So, regardless of the general speed recommendations on the autobahn, trucks over 3.5 tons must not exceed 80 km/h to maintain safe traffic flow and reduce accident risks.