Except for EMD and FM, the other companies had built steam locomotives in the past. Of the companies mentioned above, only EMD remains today. Counting all builders, about 9000 cab units were constructed from the thirties to the sixties. The diesel is therefore much more fuel efficient. B. Diesels develop maximum horsepower and efficiency over a wide range of speeds.
Steamers have a very narrow speed range in which they reach full efficiency.
This means that 1 unit can control many other units. This allows once crew per train and greatly reduces labor costs. D. Dynamic Braking allows good speed control on downgrades and reduces brake repairs. Longer trains are also allowed with better speed control. E. Maintenance costs are very low in comparison to steamer.