René B.M. De Koster

Erasmus University Rotterdam | EUR · Rotterdam School of Management (RSM)

Autonomous mobile robots (AMR) are currently being introduced in many intralogistics operations, like manufacturing, warehouses, cross-docks, terminals, and hospitals. Their advanced hardware and control software enable decentralized decision-making processes and thereby autonomous operations in dynamic environments. These developments have influen...

Purpose: Warehouses are under pressure to operate as efficiently as possible. In pursuit of attaining high efficiency in the order picking process, the warehouse manager must take several planning decisions, typically supported by a central planning system. However, highly centralised work erodes the autonomy of warehouse workers, interfering with...

Order picking is a physically demanding, time-consuming, and costly process in most warehouses. To make the process more efficient, recently, ride-on autonomous robotic order pick trucks (collaborative robots or cobots) have been introduced, that assist the order picker. The order picker can ride on the cobot to travel large distances, but when pic...

Autonomous mobile robots are increasingly used for order picking, order delivery, and parcel sorting. This article studies a robotic sorting system that uses robots to transport parcels from loading stations to drop‐off points. While this system provides more flexible throughput capacity than conventional sorting systems, its performance is signifi...

Multi-tote storage and retrieval (MTSR) autonomous mobile robots can carry multiple product totes, store and retrieve them from different shelf rack tiers, and transport them to a workstation where the products are picked to fulfill customer orders. In each robot trip, totes retrieved during the previous trip must be stored. This leads to a mixed s...

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...

Order picking is a critical and resource-intensive process within warehouse operations. Many warehouses still heavily rely on human operators for picking orders. However, human order pickers have become a scarce resource, partly due to the physically demanding nature of the order picking process. If warehouses want to remain competitive, they shoul...

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...

Autonomous vehicle storage and retrieval systems have greatly increased in popularity in the last decade. In such a system, at each tier multiple roaming vehicles transport totes between the storage locations and the lifts. However, this may lead to vehicle interference. We study in which order and by which vehicle the storage and retrieval request...

Many warehouses involved in e-commerce order fulfillment use robotic mobile fulfillment systems. Because demand and variability can be high, scheduling orders, robots, and storage pods in interaction with manual workstations are critical to obtaining high performance. Simultaneously, the scheduling problem is extremely complicated because of intera...

When scheduling the distribution of ordered items from a warehouse to customers, the transportation planning is generally done first and serves as input for planning warehouse operations. Such a sequential approach can lead to substantial inefficiencies when the customer deliveries are restricted by time windows and the warehouse has limited resour...

Robotisation is increasing in warehouse operations, but human employment continues to be relevant. Traditionally manual activities, such as order picking, are being re-designed into collaborative human–robot tasks. This trend exemplifies the transition towards a human-centric Industry 5.0, focusing on synergy instead of seeking human replacement. H...

Puzzle-based storage (PBS) systems store unit loads at very high density, without consuming space for transport aisles. In such systems, each load is stored on a moving device (conveyor module or transport vehicle), making these systems very expensive to build and maintain. This paper studies a new type of PBS system where loads are moved by a smal...

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)...

Warehousing operations are crucial in any supply chain, as they decouple demand and supply in time, space, and quantity. Automation has gradually changed the type and nature of operations. The first fully automated warehouse system, a so-called AS/R system, was introduced in the 1960s by Demag. Since then, warehouses have changed substantially. New...

Deep-lane shuttle-based storage systems with forklifts are widely used in bulk storage and finished-goods warehouses that require dense storage paired with high operational efficiency. In such a system, automated shuttles take care of the movements of loads within the storage lanes, and forklifts take care of the horizontal and vertical movements o...

An upward line extension is a new, improved product within an existing product category for the high-end market. Many manufacturers pursue line-extension strategies, but they carry risks due to uncertain consumer taste, the internal competition between products, and the external competition between firms. We use game theory to answer when a firm sh...

For nearly two decades, ocean carriers have been locked in an arms race for capacity, which has led to huge losses for many and even bankruptcy for some. We investigate the nature of this investment race by studying a long-term capacity investment problem in a duopoly under demand uncertainty. In our model, two firms make sequential capacity decisi...

Purpose In manual order picking systems, temporary workers are often employed to handle demand peaks. While this increases flexibility, it may hamper productivity, as they are usually unfamiliar with the processes and may have little experience. It is important for managers to understand how quickly inexperienced workers arrive at full productivity...

Warehouses are becoming increasingly robotized. Autonomous rack-climbing robots have recently been introduced in e-commerce fulfillment centers. The robots not only retrieve loads from any level in a rack but also, roam the warehouse and bring the loads to order picking stations without using conveyors or lifts. This paper models and analyzes this...

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...

Multi-tote storage and retrieval (MTSR) autonomous mobile robots (AMRs) can carry multiple product totes, store and retrieve them from different shelf-rack tiers, and transport the retrieved totes to a workstation where the products are picked to fulfill customer orders. In each robot trip, totes retrieved in the previous trip must be stored. This...

An upward line extension is a new, improved product within an existing product category for the high-end market. Many manufacturers pursue line-extension strategies, but they carry risks due to uncertain consumer taste, the internal competition between products (represented by the firm's profitability for the line extension), and the external compe...

At the core of every high-performing warehouse is an efficient order picking (OP) system. To attain such a system, policy choices should be carefully aligned with subjects responsible for the actual picking within the established system. Despite recent advancements in automating the picking process due to Industry 4.0, human operators will continue...

Puzzle-based systems store unit loads in very high density without consuming space for transport aisles. In such systems, each load is stored on a moving device (conveyor module or transport vehicle), making these systems very expensive to build and maintain. This paper studies a new type of PBS system where loads are moved by a small number of aut...

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...

Collaboration in warehousing has the potential to decrease warehousing costs and increase supply chain efficiency and is therefore popular in practice. However, there is little literature quantifying the benefits of warehouse collaboration. In this paper, we study the impact of collaboration on two main internal resources of the warehouse; order pi...

The COVID-19 pandemic has caused global economic turmoil. Although many companies have suffered huge losses, some have flourished by changing their old ways of doing business. We investigate the business transformation process under drastic market changes and time pressure, with a focus on decision speed and structure in the decision & planning pha...

Many distribution centers use expensive, conveyor-based sorting systems that require large buildings to house them. In areas with tight space, robotic sorting systems offer a new type of solution to sort parcels by destination. Such systems are highly flexible in throughput capacity and are now gradually being introduced, particularly in express co...

This paper studies puzzle-based storage (PBS) systems with multiple simultaneously movable empty cells and with block movement (i.e. multiple loads in a line can move simultaneously). Simultaneous movement can potentially reduce the retrieval time substantially, but have not yet been rigorously studied. Our aim is to determine the minimum number of...

The COVID-19 pandemic has caused global economic turmoil. Although many companies have suffered huge losses, some have flourished by changing their old ways of doing business. We investigate the business transformation process under drastic market changes and time pressure, with a focus on decision speed and structure in the decision & planning pha...

Cross-efficiency measurement is an extension of Data Envelopment Analysis that allows for tie-breaking ranking of the Decision Making Units (DMUs) using all the peer evaluations. In this article we examine the theory of cross-efficiency measurement by comparing a selection of methods popular in the literature. These methods are applied to performan...

In e-commerce fulfilment centres, storage assignment is critical to ensure short response times. To achieve this, many online retailers have moved to product dispersion in combination with product turnover-based slotting. However, commonly used policies do not fully utilise the historical customer demand information to optimise the storage assignme...

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...

Many operations are characterized by a trade-off between speed and quality. This calls for an exploration of effective strategies to balance the two metrics. This paper investigates the separate and joint effect of quantity and quality feedback on both performance metrics in order picking. We collected data from two real-effort experiments with in...

The daily medicine delivery is one of the most important activities in hospitals. The traditional medicine delivery, from hospital warehouses to the patients, typically involves a human delivery team supplying patients by handcarts. The multiple steps in the medicine delivery process impact the efficiency and increase the risk of contamination. Man...

Scheduling the availability of order pickers is crucial for effective operations in a distribution facility with manual order pickers. When order-picking activities can only be performed in specific time windows, it is essential to jointly solve the order picker shift scheduling problem and the order picker planning problem of assigning and sequenc...

Order picking is one of the most demanding activities in many warehouses in terms of capital and labor. In parts-to-picker systems, automated vehicles or cranes bring the parts to a human picker. The storage assignment policy, the assignment of products to the storage locations, influences order picking efficiency. Commonly used storage assignment...

Autonomous mobile robots (AMR) are currently being introduced in many intralogistics operations, like manufacturing, warehousing, cross-docks, terminals, and hospitals. Their advanced hardware and control software allow autonomous operations in dynamic environments. Compared to an automated guided vehicle (AGV) system in which a central unit takes...

For over 10 years, container shipping lines have been locked in an arms race for capacity, which has led to huge losses for many carriers and even bankruptcy for some. We investigate the dynamics of this investment race by studying a long-term capacity investment problem in a competitive market under demand uncertainty. In our model, two firms make...

Storage and retrieval automation has progressed rapidly. One such popular storage and retrieval system deploys two passing aisle-bound cranes. Each crane can access every location in the rack. To pass the other crane and prevent collision, each crane has to timely move the platform to an appropriate level and simultaneously rotate it. We develop a...

Storage and retrieval automation has progressed rapidly. One such popular storage and retrieval system deploys two passing aisle-bound cranes. Each crane can access every location in the rack. To pass the other crane and prevent collision, each crane has to timely move the platform to an appropriate level and simultaneously rotate it. We develop a...

Container terminals play an important role in the transportation of containerized goods in global supply chains. The number of containers handled in container terminals has increased astronomically. To accommodate and handle the increasing number of containers entering and leaving container terminals, their layout has seen several changes. New layo...

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...

We study a recently introduced smart compact automated parking system (CAPS), deploying straddle carriers, which require little footprint area. The straddle carriers can elevate and move a car over other cars in the horizontal direction in deep storage lanes, thereby considerably increasing the car storage capacity. Customers can reserve a parking...

This editorial explores research opportunities of operations management due to special characteristics of online-to-offline ecommerce. Representative contributions collated in this special issue are summarized. Through these research efforts and achievements, we highlight challenges for future exploration.

Warehouses are an inevitable component in any supply chain and a vividly investigated object of research. Much attention, however, is absorbed by warehousing systems dedicated to the special needs of online retailers in the business-to-consumer segment. Due to the ever increasing sales volumes of e-commerce this focus seems self-evident, but a much...

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...

Customer order response time and system throughput capacity are key performance measures in warehouses, which depend strongly on the storage strategies deployed. One popular strategy is to split inventory into a bulk storage and a pick stock, or forward-reserve (FR) storage. Managers often use a rule of thumb: when the ratio m of average picks per...

In “Capacity Analysis of Sequential Zone Picking Systems” by van der Gaast, De Koster, Adan, and Resing, a capacity model for sequential zone picking systems is developed. These systems are popular internal transport and order-picking systems in practice. The major disadvantage of such systems is congestion and blocking under heavy use, leading to...

Storage automation has progressed rapidly the last decades, also in hospitals and pharmacies. One such popular storage and retrieval system deploys two passing aisle-bound cranes. Each crane can access every location in the rack. To pass the other crane and prevent collision, each crane has to timely move the pick platform to an appropriate positio...

Many cities struggle with space shortage for parking and transportation activities. We model and analyse a recently introduced smart compact automated parking system (CAPS), deploying straddle carriers, which require little footprint area. The straddle carriers can elevate and move a car over other cars in the horizontal direction in deep storage l...

Container terminals play a major role in the growth of international trade. They need to accommodate the increasing number of containers although their space is limited, particularly close to major cities. One approach, often used in practice, is horizontal expansion through expensive land reclamation projects. In contrast, vertical expansion uses...

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...

This study illustrates the relevance and importance of incorporating safety constraints, picker blocking, and vertical travel due to high level storage locations when developing order picking systems (i.e., deciding on zoning, storage, batching, and routing). Results show that safety constraints induce wait times, and cause additional traveling, pi...

We study the integrated problem of allocating containers and scheduling a yard crane in a block with multiple input/output (I/O) points. The crane moves each storage container from an I/O point to a location selected from a set of open locations. A location may be suitable to stack different containers. The crane moves retrieval containers from ret...

Scheduling trucks and assigning them to dock doors are two major operational decisions at cross-dock facilities. Including flexibility by operating (part of)the dock doors in a mixed service mode is known to make cross-dock operations more efficient (i.e., when both inbound and outbound trucks can be processed at these mixed-mode doors). However, t...

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...

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...

Sequential zone picking systems are popular conveyor-based picker-to-parts order picking systems that divide the order picking area in work zones. When designing a zone picking system, it is important to know whether the throughput capability of the system can meet customer demand. However, the performance and maximum throughput capability of a zon...

Many cities have implemented delivery time windows, which limit city center access for freight vehicles. Each city determines its time windows independently. However, time window restrictions of one city also affect store deliveries in neighbouring cities, since retailers combine deliveries to customers in different cities in a single trip. We deve...

We investigate the impact of investments in delivery service with one or two major competing online retailers. Customers diffuse among the retailers, based on purchasing experience and online reviews (i.e., social network). Firms decide on investments aimed at maximizing profit. For both Nash and Stackelberg competition cases, the effect on market...

Compact automated parking (CAP) systems are fully automated parking systems, which store cars densely. Such systems are mainly used in congested cities all over the world, providing rapid parking access and safe vehicle storage. We study a prominent new technology, with relatively low cost and rapid response. The system has a rotating ring equipped...

E-commerce fulfillment competition evolves around cheap, speedy, and time-definite delivery. Milkrun order picking systems have proven to be very successful in providing handling speed for a large, but highly variable, number of orders. In this system, an order picker picks orders that arrive in real time during the picking process; by dynamically...

E-commerce retailers face the challenge to assemble large numbers of time-critical picking orders each consisting of just a few order lines with low order quantities. Traditional picker-to-parts warehouses are often ill-suited for these prerequisites, so that automated warehousing systems (e.g., automated picking workstations, robots, and AGV-assis...

More and more retailers allow customers to order goods online and then pick them up in a store. In this setting, these orders are typically served from a dedicated warehouse. This often means that the stores are visited by different vehicles to replenish the store inventory and to supply the pick-up points. Motivated by a collaboration with an omni...