If trains use diesel engines to power electric motors, why don't trucks do the same?

Trains commonly use a setup known as diesel-electric propulsion, where a diesel engine drives an electric generator. The electricity generated is then used to power electric motors that drive the train's wheels. This system offers several advantages for trains.

Diesel engines are renowned for their ability to produce high levels of torque, making them suitable for heavy-duty applications like hauling heavy loads. By utilizing the diesel engine to generate electricity and then power electric motors, trains can benefit from the robust torque output of the diesel engine while enjoying the advantages of electric propulsion.

Also diesel engines are known for their fuel efficiency, especially when operating at a constant speed, which is common for trains on long-distance routes. By employing the diesel-electric setup, trains can achieve better overall fuel efficiency compared to traditional mechanical transmission systems.

Diesel-electric propulsion allows for improved noise and vibration control. By isolating the diesel engine from the wheels, vibrations and noise can be minimized, resulting in a smoother and quieter ride for passengers.

On the other hand, trucks generally rely on direct mechanical power transmission from the diesel engine to the wheels. Trucks operate in a more constrained environment compared to trains. The additional components required for diesel-electric propulsion, such as the electric motors and generators, would add weight and take up valuable space within the truck's chassis. This can impact payload capacity, maneuverability, and overall cost-effectiveness for trucking companies.

Unlike trains that typically operate at a relatively constant speed on dedicated tracks, trucks frequently encounter varying traffic conditions, including frequent stops and starts. Direct mechanical power transmission provides more immediate control over the vehicle's acceleration and responsiveness, which is crucial in these dynamic operating conditions.

There are ongoing advancements in electric and hybrid technologies for trucks, especially for urban and short-haul applications. Some manufacturers are exploring the use of electric or hybrid powertrains in trucks to address environmental concerns and improve fuel efficiency. But, the transition to widespread adoption of such systems in the trucking industry is a gradual process that involves various technical, economic, and infrastructural considerations.