There is no single answer to the question of what is the fastest semi-truck in the world. It depends on a variety of factors, including the type of engine, aerodynamics, and gearing. While some semi-trucks have reached speeds as high as 150 mph (241 km/h), these vehicles are not typically used for long-distance hauling and are usually used for short trips or drag racing.
The fastest diesel semi-truck in the world is the Peterbilt 379X. This vehicle was tested in 2008 at Bonneville Salt Flats in Utah, where it achieved a top speed of 173 mph (278 km/h). It was powered by a 2,300 horsepower engine and featured an aerodynamic design that allowed it to reduce wind resistance and reach higher speeds.
Another contender for the title of fastest semi-truck is the Freightliner Cascadia. This vehicle was tested at a closed course in Nevada in 2018 and achieved a top speed of 127 mph (204 km/h). It was powered by an 850 hp engine and featured an aerodynamic design to reduce wind resistance.
These two vehicles are not available for purchase by consumers, but they demonstrate what is possible with modern technology. There are many semi-trucks that can reach high speeds on highways, but they must adhere to speed limits set by local laws. The highest speed limit for commercial trucks on certain highways can be up to 75 mph (121 km/h) depending on where they are located.
Conclusion: The Peterbilt 379X holds the record for fastest diesel semi-truck in the world, reaching a top speed of 173 mph (278 km/h). On public roads, however, trucks must adhere to speed limits set by local laws which rarely exceed 75 mph (121 km/h).
