Why is the efficiency of a diesel locomotive higher than the efficiency of a steam locomotive?

In order to find out why the efficiency of a diesel locomotive is greater than the efficiency of a steam locomotive, we begin by recalling the definitions of the efficiency.

Efficiency is the ratio of the energy used to transport the cargo to the energy received.

The locomotive has an internal combustion engine, which is always more efficient than a steam engine.

The steam engine generates energy in the furnace of a steam boiler, and then it moves into the cylinder and piston, while there is a loss of energy.

In a diesel locomotive, energy is generated where it is used – in the engine cylinders.
We conclude that there are no energy losses associated with the transportation of energy from the place where it is obtained to where it is used affects the efficiency.