Push-Pull: Missing the Woods for the Trees?

After the successful haulage of train number 22221/22222 Mumbai CSMT CSMT-Nizamuddin Rajdhani Express by twin locos (one loco in front, and one loco in rear) in push-pull mode, IR has proposed to extend this to other Rajdhanis as well.

The reason cited being higher average speeds due to faster acceleration and deceleration of the push-pull configuration

While this is commendable for these prestigious trains, the Indian Railways should pause a while and consider whether these may actually be the wrong class of trains which are being prioritized for this format.

Rajdhanis get the maximum priority over other trains along their path besides having a minimum number of halts.

This means that a Rajdhani is able to run most of the time at the maximum permissible speeds without frequent acceleration/deceleration

Hence the push-pull configuration is less beneficial to Rajdhanis than those trains which halt at say every 40 odd kilometres on an average and is hauled end-to-end by an electric loco.

A classic example of this is the Howrah Delhi Kalka Mail which travels 1712 km with 37 intermediate halts (average halt distance is 46.2 km).

Hence, such trains with a larger number of halts or path issues should get priority in getting the push-pull haulage format.

Also if Indian Railways wishes to achieve higher average speeds for trains running in fully unelectrified territory, they might use the push-pull mode using 2 Diesel locos.

However, the push-pull format is not feasible for trains which run in both electrified and unelectrified territory from origin to destination.

In addition, the short and medium distance intercity and mail/express trains also need a higher degree of punctuality due to a large number of commuters travelling in such trains.

For this, Indian Railways may re-configure the WAP-4 locos making them fit for push-pull working.

This could be done in addition to IR’s decision to ramp up production of three-phase locos.

Push-pull is also beneficial for increasing the average speeds in sections where the maximum permissible speeds cannot be increased due to constraints such as lack of availability of land, funds and technology.

Most sections on IR are not fenced, yards at major stations still pose path and speed challenges due to congestion, sharp turnouts and dilapidated cement concrete aprons.

Moreover, there are numerous permanent and temporary speed restrictions along a train’s path which hampers average speed.

In sum, push-pull is extremely beneficial, for all fully electric hauled mail/exp/SF/Intercity trains.

Image credit: Amol Nikam

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About the Author: Khalid Kagzi

3 Comments

  1. Well the author has put it very correctly, but if LHB rakes are important criteria for running push-pull then would it be right to use P4s for such trains without HOG facility?

  2. I am not sure your explanation that slower trains with more stop will benefit more than Rajdhanis. The most important reason for this in my view is that the cause for reduction in speed is far more often due to congestion resulting in running continously under caution signals, and then comes from temporary or permanent speed restrictions. These factors affect a train like a Rajdhani far more, since its more likely to have passed through at its MPS if that had not been the case. Now a train with far more stops has a higher chance of just passing these by at less than MPS and also because it is likely to have more stops to allow faster trains to overtake.

    Another important reason why a faster train like a Rajdhani is affected more is simply due to its higher MPS. Thus allowing it to accelerate faster to its MPS means any time loss in the schedule.

    Of course, one truly has to do simulation runs to understand how this would work.

    As for looking at WAP4s, think its is pointless. Now it is the WAP7 which is anyway the mainstay of IR passenger services. As of start of December 911 WAP7 were working compared to 772 WAP4. Of the 911 WAP7s, 269 were commissioned since April 2019. At the rate of production, by Dec 2020 there will probably be 1300 WAP7s and about 750 WAP4s.

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