Debjit Roy

Indian Institute of Management | IIM · Area of Production and Quantitative Methods

In many countries, vehicle replacement policies are implemented to reduce the average age of the vehicles on the road. Through these policies, policymakers typically aim to reduce emissions and to stimulate demand for automobiles through vehicle renewal. Not much is known however, about the more detailed operational consequences of vehicle age in t...

Problem definition: Online food delivery (OFD) platforms have transformed the restaurant industry, prompting restaurateurs to serve both online and dine-in customers. To ease pressure on store-front kitchen capacity, restaurateurs use channel control and central kitchen strategies. Channel control determines when to close the OFD channel, while cen...

This study investigates the effect of safety-specific transformational leadership (SSTL) on the performance outcomes of safe driving and driving productivity in both long and short-haul truck cargo transport. We conduct our study in the context of a hazardous material (HAZMAT) Indian transport company using a sample of 1,196 trips across 104 unique...

During the last decade, several retailers have started to combine traditional store deliveries with the fulfillment of online sales to consumers from omni‐channel warehouses, which are increasingly being automated. A popular option is to use autonomous mobile robots (AMRs) in collaboration with human pickers. In this approach, the pickers' unproduc...

The case tracks Dineout's evolution into a full-scale tech solution provider for restaurants. In 2020, the COVID-19 pandemic struck the world. Several countries, including India, implemented complete lockdowns to control the spread of the virus. Stringent measures to ensure social distancing, night curfews and restrictions on social gatherings cont...

Mahindra Trucks and Buses forayed into India's commercial vehicles sector in 2005. However, they had to battle numerous supply chain challenges associated with introducing a new product (a new truck brand) in the market and to gain a noticeable foothold in the market. In this case, we attempt to align customer brand stickiness with the supply chain...

Freight transportation has been experiencing a renaissance in data sources, storage, and dissemination of data to decision makers in the last decades, resulting in new approaches to business and new research streams in analytics to support them. We provide an overview of developments in both practice and research related to big data analytics (BDA)...

We consider the setting of a firm operating multiple warehouses and multiple stores where each warehouse is endowed with an initial non-replenishable inventory. There is a finite selling horizon and, at the beginning of each period, the firm needs to decide for each store how many units of inventory to replenish from each warehouse together with th...

Global adoption of electric vehicles (EVs) faces many challenges such as range anxiety, high cost of EVs, and inadequate charging infrastructure. EV-sharing platforms resolve such concerns by setting up an optimal configuration for charging infrastructure and optimizing the charging decisions for depleted EVs. These platforms manage the vehicles’ f...

With the growth of ocean transport and with increasing vessel sizes, managing congestion at the landside of container terminals has become a major challenge. The landside of a sea terminal handles containers that arrive or depart via train or truck. Large sea terminals have to handle thousands of trucks and dozens of trains per day. As trains run o...

Smart technologies and increased data availability enable restaurateurs to gather more information about customers and their behavior. These data can be combined with data from other sources to make a wide range of strategic and operational restaurant decisions, and can therefore generate tremendous value for restaurants and their customers. This s...

In the future, vehicle sharing platforms for passenger transport will be unmanned, autonomous, and electric. These platforms must decide which vehicle should pick up which type of customer based on the vehicle’s battery level and customer’s travel distance. We design dynamic vehicle allocation policies for matching appropriate vehicles to customers...

We study the operational problem of loading and unloading trains at a container terminal. Trains are served by two gantry cranes which spread over multiple trains on parallel tracks at the terminal landside. Multiple straddle carriers are available to move containers between the stacking area and drop off locations perpendicular to the train tracks...

For an e-hailing taxi operation, we analyse a driver's profit-maximising reactive strategy (to either accept or refuse a ride request) in response to the ride request broadcast by the platform. We analyse four operating modes, each of which is a combination of either of two reactive strategies: no refusal and refusal based on proximity, and either...

Online Technical Appendix for “Arulanantha Prabu Ponnachiyur Maruthasalam, Debjit Roy & Prahalad Venkateshan (2021): Modelling driver’s reactive strategies in e-hailing platforms: an agent-based simulation model and an approximate analytical model, International Journal of Production Research, DOI: 10.1080/00207543.2021.1987554”

A Robotic Mobile Fulfillment System (RMFS) is an automated parts-to-picker material handling system, in which robots carry pods with products to the order pickers. It is particularly suitable for e-commerce order fulfillment and can quickly and frequently reallocate workers and robots across the picking and replenishment processes to respond to str...

Until recently, architects planned the layout for a new hospital based only on design aspects, experience, and legal regulations. Today, hospital logistics planners are included at an earlier stage in the project and support hospital layout planning with important logistics aspects. While methods supporting patient flow are prioritized in the layou...

Achieving timely last-mile order delivery is often the most challenging part of an e-commerce order fulfillment. Effective management of last-mile operations can result in significant cost savings and lead to increased customer satisfaction. Currently, due to the lack of customer availability information, the schedules followed by delivery agents a...

Due to demanding service levels in e‐commerce order fulfillment, modeling and analysis of integrated storage and order picking processes in warehouses deserve special attention. The upstream storage system can have a significant impact on the performance of the downstream order picking process. With a particular focus on multiline e‐commerce orders...

Warehouse automation is increasingly adopted to manage throughput fluctuations in e‐commerce order fulfillment. This work develops queuing network models and solution methodologies for performance analysis of a stock‐to‐picker system that connects an upstream automated storage system to a downstream pick station. We focus on the pick station proces...

Bulk-service multi-server queues with heterogeneous server capacity and thresholds are commonly seen in several situations such as passenger transport or package delivery services. In this paper, we develop a novel decomposition-based solution approach for such queues using arguments from renewal theory. We then obtain the distribution of the waiti...

Many intra-logistics systems, such as automated container terminals, distribution warehouses, and cross-docks, observe parallel process flows, which involve simultaneous (parallel) operations of independent resources while processing a job. When independent resources work simultaneously to process a common job, the effective service requirement of...

Multi-stage semi-open queuing networks (SOQNs) are widely used to analyze the performance of multi-stage manufacturing systems and automated warehousing systems. While there are several methods available for solving single-stage SOQNs, solution methods for multi-stage SOQNs are limited. Decomposition of a multi-stage SOQN into single-stage SOQNs an...

New container terminals are embracing robotized transport vehicles such as lift-automated guided vehicles (LAGVs) and automated guided vehicles (AGVs) to enhance the terminal throughput capacity. Although LAGVs have a high container handling time, they require less coordination with other terminal equipment in comparison with AGVs. In contrast, AGV...

The design of container terminal operations is complex because multiple factors affect operational performance. These factors include numerous choices for handling technology, terminal topology, and design parameters and stochastic interactions between the quayside, stackside, and vehicle transport processes. In this research, we propose new integr...

POM Special Issue CFP: Managing Autonomous and IoT-driven Intralogistics Operations

Autonomous vehicle-based storage and retrieval systems are commonly used in many fulfillment centers (e.g., e-commerce warehouses), because they allow a high- and flexible-throughput capacity. In these systems, roaming robots transport loads between a storage location and a workstation. Two main variants exist: horizontal, where the robots only mov...

Robotic handling systems are increasingly applied in distribution centers. They require little space, provide flexibility in managing varying demand requirements, and are able to work 24/7. This makes them particularly fit for e-commerce operations. This paper reviews new categories of automated and robotic handling systems, such as shuttle-based s...

A Robotic Mobile Fulfillment System is a recently developed automated, parts-to-picker material handling system. Robots can move storage shelves, also known as inventory pods, between the storage area and the workstations and can continually reposition them during operations. This paper shows how to optimize three key decision variables: (1) the nu...

The robotic mobile fulfillment system (MFS) is widely used for automating storage pick and pack activities in e-commerce distribution centers. In this system, the items are stored on movable storage shelves, also known as inventory pods, and brought to the order pick stations by robotic drive units. We develop stylized performance evaluation models...

Order release policies such as a card-controlled CONWIP policy aim to improve system responsiveness and minimize system-wide inventory levels. It is not clear if order release policies (without card control) can be equally effective under certain settings of the production system design parameters. In this research, we study the performance of alte...

In many warehouses shuttle-based technologies have replaced the traditional AS/R system based storage technologies. The impact these systems have on downstream order picking performance is largely unknown. To study the interactions between upstream storage and downstream picking systems, we develop a novel analytical model for integrated storage an...

The case focuses on truck high idle time, truck detention, and enroute challenges faced by Nagpur Golden Transport Company, a trucking company with a fleet size of 150 trucks. Being in a highly competitive market, every single order not fulfilled by the transporter is an opportunity lost. How should NGTC use GPS data, MIS, and other freight transpo...

Takshshila, the owner of Sandwichworkz, a trendy restaurant in Ahmedabad, India, is worried about the diminishing profitability of her restaurant. Recent promotional offers have increased the footfall, but not profitability. To address this issue, she knew she had to optimize and redesign their menu. She also realizes that to properly address this...

We study proactive and reactive sea-based order-fulfillment decisions for a set of SKUs. In such systems, a proactive strategy may be more costly than a reactive strategy and variable marginal costs change with respect to an activity profile. We derive the optimal sets of SKUs and their quantities to handle prior (proactive strategy) or after (reac...

In many service industries, customers have to wait for service. When customers have a choice, this waiting may influence their service experience, sojourn time, and ultimately spending, reneging, and return behavior. Not much is known however, about the system-wide impact of waiting on customer behavior and resulting revenue. In this paper, we empi...

Several white goods companies are grappling with issues such as short product life-cycle and high item obsolescence rates. This case analyzes several strategies to overcome item obsolescence, standardize put-away and picking operations and overcome challenges with low picker efficiency at white-goods warehouses.

Semi-open queuing networks (SOQNs) are widely applied to measure performance of manufacturing, logistics, communications, restaurant, and health care systems. Many of these systems observe variability in the customer arrival rate. Therefore, solution methods, which are developed for SOQNs with time-homogeneous arrival rate, are insufficient to eval...

Warehouse design and operations have undergone major changes over the past decades. In particular, with the onset of e-commerce, the complexity of warehouse operations has increased multi-fold with the storage of large SKU assortment in small quantities, volatile demand patterns and primarily single-line customer orders. They have grown in size due...

Pallets are fundamental assets critical to worldwide supply chain logistics. This research develops models for closed-loop pallet pooling providers to understand the environmental and economic impact of customer characteristics and design options. First, an analytical model is developed to quantify the effects of repair facility location and pallet...

With the growing worldwide trade, container terminals have grown in number and size. To increase operational efficiency, many new terminals are now automated. The key focus is on improving seaside processes, where a distinction can be made between single quay crane operations (all quay cranes are either loading or unloading containers) and overlapp...

To improve operational flexibility, throughput capacity, and responsiveness in order fulfillment operations, several distribution centers are implementing autonomous vehicle-based storage and retrieval system (AVS/RS) in their high-density storage areas. In such systems, vehicles are self-powered to travel in horizontal directions (x- and y- axes),...

In developing countries, truck purchase cost is the dominant criteria for fleet acquisition-related decisions. However, we contend that other cost factors such as loss due to the number of en route truck stoppages based on a truck type and recovery cost associated with a route choice decision, should also be considered for deciding the fleet mix an...

New container terminal technologies such as passing dual yard cranes per stack promise increase in stacking throughput capacity. However, dual yard cranes can interfere, which reduces the cranes’ throughput capacity. Using crane operational protocols, we develop a stochastic model for two passing dual yard cranes and obtain closed-form expressions...

Having a good estimate of a vessel’s handling time is essential for planning and scheduling container terminal resources, such as berth positions, quay cranes (QCs) and transport vehicles. However, estimating the expected vessel handling time is not straightforward, because it depends on vessel characteristics, resource allocation decisions, and un...

Using GPS data of 370 long-haul trips in India, survey data of 49 truck drivers, and ERP data, this study examines the role of driver personality characteristics in predicting risky and productive driving. The results show that more conscientious drivers display more risky driving behavior. More extravert drivers are less productive, whereas driver...

We propose a novel semiopen queuing network (SOQN) model for the interterminal transportation (ITT) problem where multiple container terminals use a common fleet of vehicles (automated lift vehicles, automated guided vehicles, multitrailers, and barges) to transport containers between terminals. To solve the overall queuing network, our solution ap...

Container terminal performance is largely determined by its design decisions, which include the number and type of quay cranes, stack cranes, transport vehicles, vehicle travel path and stack layout. We investigate the orientation of the stack layout (parallel or perpendicular to the quayside) on the throughput time performance of the terminals. Pr...

Shuttle-based compact systems are new automated multideep unit-load storage systems with lifts that can potentially achieve both low operational cost and large volume flexibility. In this paper, we develop novel queuing network models to estimate the performance of both single-tier and multitier shuttle-based compact systems. Each tier is modeled a...

The existing industry strategies for managing pallets, (single-use expendable pallets, buy/sell programs, and leased pallet pooling programs), are analyzed and compared using push and pull inventory control policies. A two-stage integrated framework is developed that combines cost relationship models with data gathered in industry with multi-echelo...

Low customer wait times at restaurants can improve both customer walk-ins and satisfaction levels. To manage customer wait times, the operators need a thorough understanding of how restaurant design parameters such as the layout, the number of tables, the number of chefs and other critical kitchen resources affect customer throughput times. In this...

This paper models Robotic Mobile Fulfillment Systems and analyzes their performance. A Robotic Mobile Fulfillment System is an automated, parts-to-picker storage system where robots bring pods with products to a workstation. It is especially suited for e-commerce distribution centers with large assortments of small products, and with strong demand...

Raymond was lagging behind in their customer order fulfillment process due to inefficiencies in their warehouse operations. Further, slotting of stock keeping units to the right bins was not in order. As a result, the warehouse capacity was limiting company's growth. This case draws lessons about how warehousing technology and scientific warehouse...

This research is the first attempt to characterize the carbon equivalent emissions associated with pallet remanufacturing operations for two repositioning scenarios (cross-docking and take-back), and under multiple levels of pallet loading and service conditions. Industry data was acquired through observation and time studies at 12 facilities in No...

Autonomous vehicles-based storage and retrieval systems (AVS/RS) have been shown to offer greater flexibility to improve cycle time and throughput capacity in the transfer of unit loads in high-density storage areas of warehouses. In these systems, loads are transferred by autonomous vehicles that move horizontally along aisles and cross-aisles wit...

In the last few decades, environmental concerns of manufacturing operations have motivated the organisations to implement green principles in different processes of the supply chain. In this paper, literature in green processes is critically reviewed to understand the process-specific green issues of the supply chain. A 10-year period (2005-2014) i...

We present a queuing theory based optimization model for determining the optimal table mix in a restaurant. The optimal table mix problem is formulated for an allotment policy in which the largest available group is allotted the table. A walk-in restaurant with tables of three different capacities is considered. It is interpreted as a system of int...

Kunvarji Group is on its way to transform from a commodity trading business to a service-driven business. To become an integrated service provider in the agri-supply chain, Kunvarji is by participating actively in procurement, trading, and now eyeing options for providing agri-storage services. Their dilemma reeled around the choice of storage that...

Agarwal Packers and Movers Limited is an example of a business that delivers superior customer service with continuous logistics design innovation. The case provides details of a leading logistics and solution provider for household goods relocation who in past was facing problems due to increase in number of customer complaints and claims and also...

Efficient handling of containers at a terminal can reduce the overall vessel sojourn times and minimise operational costs. The internal transport of containers in these terminals is performed by vehicles that share a common guide path. The throughput capacity of a terminal may increase by increasing the number of vehicles; however, simultaneously c...

Capturing the waiting times (at an external queue) for a customer to access a movable resource is an important step towards measuring customer service and system performance in manufacturing, logistics, communication and health care systems. Such waiting time measures are typically used for sizing resource and buffer capacities, and thereby minimis...

This study develops an off-site emergency response plan for a nuclear power plant in Gujarat, India subject to time constraints with resource limitations and risk of radiation exposure to victims. We formulate an optimization model to capture the effect of delay in evacuation, limited resource availability, and costs associated with resource alloca...

Owing to a rapid growth in world trade and a large increase in the flow of containerized goods, sea container terminals play a vital role in globe-spanning supply chains. Container terminals should be able to handle large ships, with large call sizes within the shortest time possible, and at competitive rates. In response, terminal operators, shipp...

Technological innovations in warehouse automation systems, such as Autonomous Vehicle based Storage and Retrieval System (AVS/RS), are geared towards achieving greater operational efficiency and flexibility that would be necessary in warehouses of the future. AVS/RS relies on autonomous vehicles and lifts for horizontal and vertical transfer of uni...

Vehicle rental providers, which operate in an uncertain environment, offer differentiated services to priority and non-priority customers. In this research, we study one such service differentiation strategy, a vehicle threshold policy, which is to hold vehicles for priority class customers in anticipation of their future arrivals. To consider the...

For overlapping operations, the ALVs may need to process an unload transaction after processing a load transaction or vice versa. In such situations, the ALVs have to move from one QC location to another QC location or from one SC location to another SC location. In this section, we adopt the analytical model from Roy and De Koster, 2015 to develop...

With growing worldwide trade, container terminals have grown in number and size. Many new terminals are now automated to increase operational efficiency. The key focus is on improving seaside processes, where a distinction can be made between single quay crane operations (all quay cranes are either loading or unloading containers) and overlapping q...

Order release policies such as card-controlled CONWIP policy aim at improving system responsiveness and minimizing system-wide inventory levels. It is not clear if order release policies (without card control) can be equally effective under certain settings of the production system design parameters. In this research, we study the performance of al...

Shuttle-based compact systems are new automated multi-deep unit-load storage systems with lifts that promise both low operational cost and large volume flexibility. In this paper, we develop novel queuing network models to estimate the performance of both single-tier and multi-tier shuttle-based compact systems. Each tier is modeled as a multi-clas...