Optimizing large scale upgradations involving movable assets

Product upgradations are common, as it is practical and economical in many cases, compared to complete replacement. Proper planning and scheduling using quantitative techniques can be helpful in the case of large-scale upgradations involving movable assets, like rolling stock. There is a possibility of doing the upgradation of the asset in multiple locations, and there are operational constraints involved in executing the process. In this paper, we propose integer programming models to optimize the execution of these types of upgrades. A case involving retrofitting of bio-toilets in Indian Railways is used as an example. Computations are done for the allocation of movable assets for retrofit in a division of Southern Railways. The central unit decides the number of items to be retrofitted in each facility and facilities to be upgraded based on the output of the optimization model. Subsequently, a model for scheduling retrofitting at a facility is also discussed. There are other problems in the industry involving other movable assets like automobile and naval vessels, where extension of these models can be useful.