Whats the pros and cons of a pulling passenger locomotive to a DMU train?

Question

Whats the pros and cons of a pulling passenger locomotive to a DMU train?

Answer 1

Indeed, as mentioned above the main advantage to DMU's are their ability to "pull" in either direction, thus saving tremendous amounts of time in running the lead locomotive around the train when heading in the other direction (thus the transit service can spend more time hauling passengers and earning as much as revenue as possible which is especially important since commuter rail is not a profitable operation).

Perhaps the biggest con with these "push-pull" operations is the controversial question of whether passengers are more exposed to grade-crossing or other collisions when something is blocking the tracks, when the train is operating in push mode and the rear passenger car is the lead unit (i.e., when the locomotive is the rear of the train).  The FRA recently did a study on this issue and came to the conclusion that passengers are perfectly safe in "push-pull" operations or at least as safe as they would be in traditional "pull" operations (i.e., when the locomotive is the lead unit).

Answer 2

The pros of a DMU (or EMU come to that) is that there is less time spent at a terminal station whilst the motive power unit runs round and couples on the the other end or another power unit is attached. In the UK this problem was overcome on hauled trains by the construction of 'DVTs' - Driving Van Trailer. This enables the loco to be controlled from a driving position at the end away from the loco. The system is mainly used on the East Coast Main Line from London, King's Cross and the line to East Anglia from Liverpool Street. All other main lines use fixed formation multiple units, electric and diesel. So there seem to be very little cons to the system.

Later: and having regard to the second answer. Here in the UK the regulatory bodies would not permit a multiple unit with an engine above the floor in a lead carriage to also carry passengers. Hence our High Speed trains which are effectively DMUS have what is classed as a loco at each end - the same with the EMU high speed trains on the East Coast line. There hasn't been a problem with DVTs leading, however, as there wasn't the perceived risk of the engine being pushed back into a carriage full of passengers. More lately, that stance has been modified with the introduction of modern stock such as the Pendolinos.

The main 'con' is that there is more flexibility in making up the train when you have hauled stock. Operators can add or remove carriages to cope with demand, including adding or removing stock such as dining and sleeping cars.