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What determines where locomotives are changed for a train?

July 17, 2019, 1:29 PM
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Locomotive changes often happen at convenient points where there is an appropriate loco shed where locos can be housed for a while and given some routine maintenance if necessary, etc. Except for long express services (for which keeping down the number of halts is a priority) hauled by WDM-2, WAM-4, WAP-4, WAP-5, and other such locos for which repair and maintenance facilities are provided at many major sheds, generally a loco will not work too far outside the territory of its home shed or zonal railway. If it breaks down too far from its territory repair crew have to be sent out from the home shed to take care of it.

Hence, the WCAM-x series locos for instance generally stay close to their home sheds even though they could be dispatched further without any problem of traction change, etc. Another point to consider is whether the loco changeover point is a convenient junction or other station where there are enough trains arriving and departing that a loco can be quickly turned around and sent back hauling another train rather than remaining unutilized for day or more, or having to be sent back light. Another consideration is whether the loco changeover point has facilities for the crew.

Of course, traction changes are often a reason to change locos too. AC locos and DC locos have to stop at the boundary between AC and DC traction regions. Electric-hauled trains, of course, have to change to diesel traction whenever they leave electrified regions.

Often, a diesel-hauled train in unelectrified territory will switch to electric traction as soon as it comes to a section that is electrified. However, this may not happen for a variety of reasons, leading to the phenomenon of diesels running under the wires for long distances: inconvenient schedules that would reduce the utilization of the loco, non-availability of a sufficient number of electric locos in the region, or the part of the route that is under the wires may be too small to justify halts to change locos when entering and leaving electrified territory.

Examples
Load, scheduling, and train priority

The Grand Trunk, Tamil Nadu, Andhra Pradesh, and Kerala Expresses are all 24 coach superfast trains, running on fairly tight schedules. Their load and halt pattern demands that no less than a WAP-4 loco will do. Their routes being fully electrified ([5/05] with the exception of Kerala’s Ernakulam – Trivandrum stretch which is diesel-hauled) the same loco hauls each all the way to New Delhi.

These trains are SCR or SR trains so naturally locos from those zones haul the trains. Earlier there weren’t as many WAP-4 locos at Arakkonam and other southern sheds, while other sheds like Jhansi had many WAP-4 locos, so these trains were often hauled by Jhansi locos rather than Erode or Arakkonam locos. However, Jhansi being a CR shed and not a terminus or traction change point for any of these trains’ routes, its locos stopped being used as soon as southern sheds like Erode, Arakkonam, and Lallaguda got more WAP-4 locos. Based on priority or on the load (number of coaches), non-superfasts and local passenger trains especially those with shorter rakes may get lower-powered or lower speed-capable locos like the WAM-4 or the old standby the WDM-2 in many cases. The really prestigious and high-priority trains that must maintain their speed and stick to their schedules, such as the Rajdhanis or Shatabdis may get the WAP-5 or WDP-4 locos, and so on.

Traction change

Some years ago on the same routes (New Delhi – Madras Central) for the Grand Trunk or Tamil Nadu, when there wasn’t through electrification, a WAM-4 from Ghaziabad (at that time the load being 21 coaches) used to haul the train until Itarsi, from where twin diesels of Itarsi or Kazipet took over and hauled the trains till Kazipet, or Vijayawada depending on the progress of electrification. Thence a WAM-4 from Vijayawada would take over again until Madras Central.

Loco links

Sometimes trains get locomotives based on a need to move the locomotives to other locations. Using such locomotives to haul a train may be more efficient (and avoid consuming a slot on the traffic schedule) than running the locomotive light back to where it is needed (and certainly more efficient than coupling it light to a train that already has an allotted locomotive). This is the reason sometimes WAP-1/WAP-4 locos haul passenger (non-superfast) trains with short rakes around Calcutta. A WDP-4 can be seen hauling the Vijayawada – Vasco Amravati Express simply because the route of the train passes through Hubli, the loco’s home shed, allowing the loco to conveniently be brought back there for maintenance. In such cases, the tra

Source – IFRCA.org

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