What is the train length of the iron dragon?

Question

What is the train length of the iron dragon?

Answer 1

Unclear to me but, going for a metaphor, they're all "iron dragons."  

As such, trains can be as long as a single locomotive or 120 cars or more.  It starts to become a self inflicted injury to operate over 9,500 feet or so (more on flat land or with DPUs), depending on ambient conditions;  the effect the temperature has on the air brake system is considerable but does allow for operation of longer iron dragons during summer months.  Train lengths tend to be kept shorter in winter months.