Alan Erera

Alan Erera
Georgia Institute of Technology | GT · School of Industrial and Systems Engineering

Ph.D. Industrial Eng and Operations Research

About

87
Publications
21,907
Reads
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2,958
Citations
Introduction
I am a Manhattan Associates/Dabbiere Chaired Professor and Associate Chair for Research in ISyE at Georgia Tech. I conduct research on data-driven decision technologies for supply chain operations and logistics problems. I develop operations research methods to address these challenges, and am interested primarily in real-time operational control problems and in planning robust systems that mitigate the impacts of operational uncertainties.
Additional affiliations
January 2001 - present
Georgia Institute of Technology
Position
  • Professor (Full)
Education
August 1996 - December 2000
University of California, Berkeley
Field of study
  • Industrial Engineering and Operations Research
September 1989 - June 1993
Princeton University
Field of study
  • Civil Engineering and Operations Resesarch

Publications

Publications (87)
Article
Full-text available
We study same-day delivery systems by formulating the Dynamic Dispatch Waves Problem (DDWP), which models a distribution center where geographically located delivery orders realize dynamically throughout the day. At each decision epoch (wave), the system's operator chooses whether or not to dispatch a vehicle route loaded with orders ready for serv...
Preprint
Full-text available
We study tactical models for the design of same-day delivery (SDD) systems. Same-day fulfillment in e-commerce has seen substantial growth in recent years, and the underlying management of such a service is complex. While the literature includes operational models to study SDD, they tend to be detailed, complex, and computationally difficult to sol...
Preprint
Full-text available
The recent proliferation of free-floating, shared micromobility systems has resulted in idle bikes and e-scooters crowding sidewalks. A key operating challenge for such systems is to determine a best distribution of these vehicles across a spatial region at any point in time to maximize system performance measured by metrics like trips served per t...
Preprint
Full-text available
Many large e-commerce retailers now have the scale to operate their own middle mile consolidation networks, moving customer shipments from stocking locations to last mile delivery partners using a private set of freight transportation loads that reduce outbound logistics cost. In this article, we study a middle mile network design problem with fixe...
Preprint
Full-text available
We study the linked tactical design problems of fleet sizing and partitioning a service region into vehicle routing zones for same-day delivery (SDD) systems. Existing SDD studies focus primarily on operational dispatch problems and do not consider system design questions. Prior work on SDD system design has not considered the fleet sizing decision...
Article
This paper presents a network design problem in the context of intra-city courier service in megacities. The considered setting is inspired by the activities of one of the main courier package companies in China. The problem consists of designing a robust yet cost-effective service network to move packages from their origins to their destinations t...
Article
Parcel logistics services play a vital and growing role in economies worldwide, with customers demanding faster delivery of nearly everything to their homes. To move larger volumes more cost effectively, express carriers use sort technologies to consolidate parcels that share similar geographic and service characteristics for reduced per-unit handl...
Article
We study the linked tactical design problems of fleet sizing and partitioning a service region into vehicle routing zones for same-day delivery (SDD) systems. Existing SDD studies focus primarily on operational dispatch problems and do not consider system design questions. Prior work on SDD system design has not considered the fleet sizing decision...
Article
Full-text available
We consider an urban instant delivery environment in which customers place orders over the course of the day and are promised delivery within a short period of time after an order is placed. The orders are fulfilled from a single facility and deliveries are made using a fixed fleet of vehicles with vehicles performing one or more delivery trips dur...
Preprint
Full-text available
With the recent boom of the gig economy, urban delivery systems have experienced substantial demand growth. In such systems, orders are delivered to customers from local distribution points respecting a delivery time promise. An important example is a restaurant meal delivery system, where delivery times are expected to be minutes after an order is...
Article
Full-text available
Rapid delivery systems where an order is delivered to a customer from a local distribution point within minutes or hours have experienced rapid growth recently and often rely on gig economy couriers. The prime example is a meal delivery system. During an operating day, couriers in such a system are used to deliver orders placed at different restaur...
Article
We design and implement decision support technology to assist dispatchers in the daily management of loadplans in less-than-truckload service networks. The freight volume that enters a service network on the day of operations deviates from the forecast freight volume used to create the loadplan. These deviations cause inefficiencies when the capaci...
Article
We study tactical models for the design of same-day delivery (SDD) systems. Same-day fulfillment in e-commerce has seen substantial growth in recent years, and the underlying management of such services is complex. Although the literature includes operational models to study SDD, they tend to be detailed, complex, and computationally difficult to s...
Article
Full-text available
The objective of this paper is to investigate the potential added value of being able to relocate production capacity, relative to fixed production capacity, in a network of multiple, geographically distributed manufacturing sites. There is a growing number of examples of production capacity that can be geographically relocated with a modest amount...
Article
Package express companies routinely operate multiple equipment types in their service networks. Nevertheless, the weekly schedule of movements used to transport packages through the network leads to changes in equipment inventory at the facility level, which will hinder their normal operations if it is not carefully taken care of. Traditional rebal...
Article
The design and control of effective sortation systems have become more complex as both the volume of parcels and also the number of time-definite service options offered by parcel carriers have grown. In this paper, we describe approaches for planning two-stage parcel sort operations that explicitly consider time deadlines and sorting capacities. I...
Chapter
This chapter introduces service network design (SND) operations research models and solution methodologies specifically focused on problems that arise in the planning of operations in the trucking, or motor freight, industry. Consolidation carriers such as less-than-truckload and package trucking companies face flow planning problems to decide how...
Preprint
Full-text available
Online restaurant aggregators have experienced significant sales growth in recent years, driving demand for meal delivery in the US. Meal delivery logistics is quite challenging, primarily due to the difficulty in managing the supply of delivery resources to satisfy dynamic and uncertain customer demand under very tight time constraints. In this pa...
Article
We study request acceptance dynamics in same-day delivery systems by formulating the Dynamic Dispatch Waves Problem with Immediate Acceptance, which models integrated management and distribution for dynamically arriving customer requests. We consider an e-commerce platform that attempts to serve most customers with same-day delivery service. When a...
Preprint
We investigate substitution-based equipment balancing for a package express carrier operating multiple equipment types in its service network. The weekly schedule of movements used to transport packages through the service network leads to changes in equipment inventory at the facilities in the network. We seek to reduce this change, i.e., the equi...
Chapter
The emergence of disruptive technologies in industrial production is one of the key features of the fourth industrial revolution that forms the foundation of super smart societies. Mobile manufacturing capacity is one such technology. The goal of this chapter is to discuss the value of production capacity mobility and existing solution methods to o...
Article
Full-text available
We analyze a problem of dynamic logistics planning given uncertain demands for a multi-location production-inventory system with transportable modular production capacity. In such systems, production modules provide capacity, and can be moved from one location to another to produce stock and satisfy demand. We formulate a dynamic programming model...
Preprint
Full-text available
We study order acceptance dynamics in same-day delivery systems by formulating the Dynamic Dispatch Waves Problem with Immediate Acceptance, which models integrated request management and order distribution for dynamically arriving requests. When a delivery request arrives, a decision is made immediately to accept (offer service) or reject (with a...
Article
We consider multistage stochastic programming problems in which the random parameters have finite support, leading to optimization over a finite scenario set. There has been recent interest in dual bounds for such problems, of two types. One, known as expected group subproblem objective (EGSO) bounds, require solution of a group subproblem, which o...
Article
This paper presents the stochastic cargo-mix problem, which aims at analysing the cargo composition needed for a liner vessel to maximise its revenue on a given service. The unreliability with respect to the demand forecast is included by considering the cargo-flows as being stochastic instead of deterministic. We also take into account accepted bo...
Preprint
We analyze the value of mobile production capacity and transshipment in a supply chain with geographically distributed production facilities and epoch-dependent demands. We describe the L location, Y mobile production unit problem as a problem of sequential decision making under uncertainty to determine transshipment, mobile production capacity rel...
Preprint
Full-text available
We consider a periodic review inventory control problem having an underlying modulation process that affects demand and that is partially observed by the uncensored demand process and a novel additional observation data (AOD) process. Letting $K$ be the reorder cost, we present a condition, A1, which is a generalization of the Veinott attainability...
Article
Dynamic ride-sharing systems enable people to share rides and increase the efficiency of urban transportation by connecting riders and drivers on short notice. Automated systems that establish ride-share matches with minimal input from participants provide convenience and the most potential for system-wide performance improvement, such as reduction...
Article
Full-text available
In this research we study the berth allocation problem (BAP) in real time as disruptions occur. In practice, the actual arrival times and handling times of the vessels deviate from their expected or estimated values, which can disrupt the original berthing plan and possibly make it infeasible. We consider a given baseline berthing schedule, and sol...
Article
The desire of companies to offer same-day delivery leads to interesting new routing optimization problems. We study the complexity of single depot dispatching problems in which a delivery to a customer must occur within a pre-specified time after the customer places the order. Thus, each order has a release date (when the order is ready for dispatc...
Article
Less-Than-Truckload (LTL) carriers operate networks of consolidation terminals, and route each customer shipment through a sequence of transfer terminals. At each terminal stop, a shipment is unloaded from an inbound trailer and reloaded onto an outbound trailer. A load plan determines the specific path of terminals to be used to transfer freight m...
Article
We study same-day delivery systems by formulating the dynamic dispatch waves problem (DDWP), which models a depot where delivery requests arrive dynamically throughout a service day. At any dispatch epoch (wave), the information available to the decision maker is (1) a set of known, open requests that remain unfulfilled, and (2) a set of potential...
Article
According to the Centers for Disease Control and Prevention, approximately 48 million people experience foodborne illnesses per year. The majority of the illnesses are attributed to the presence of bacteria in food products. However, there is some concern about the likelihood of food contamination resulting from intentional acts of sabotage. This r...
Article
The intent of this research is to generate a set of non-dominated finite-memory policies from which one of two agents (the leader) can select a most preferred policy to control a dynamic system that is also affected by the control decisions of the other agent (the follower). The problem is described by an infinite horizon total discounted reward, p...
Preprint
Full-text available
We study same-day delivery (SDD) distribution systems by formulating the Dynamic Dispatch Wave Problem (DDWP), which models a depot where delivery requests arrive dynamically throughout a service day. At any dispatch epoch (wave), the information available to the decision maker is (1) a set of known, open requests which remain unfulfilled, and (2)...
Article
We consider a leader-follower partially observed Markov game (POMG) and analyze how the value of the leader’s criterion changes due to changes in the leader’s quality of observation of the follower. We give conditions that insure improved observation quality will improve the leader’s value function, assuming that changes in the observation quality...
Article
The deliberate contamination of food is well recognized as a major public health threat. A food supply chain offers several possible targets for the intentional insertion of a biological or chemical toxin by a perpetrator, which can result in significant morbidity and mortality. We assume that both manager (defender) of the food production facility...
Article
Full-text available
In this work, we study the single machine scheduling problem with uncertain release times and processing times of jobs. We adopt a robust scheduling approach, in which the measure of robustness to be minimized for a given sequence of jobs is the worst-case objective function value from the set of all possible realizations of release and processing...
Preprint
Dynamic ride-sharing systems enable people to share rides and increase the efficiency of urban transportation by connecting riders and drivers on short notice. Automated systems that establish ride-share matches with minimal input from participants provide the most convenience and the most potential for system-wide performance improvement, such as...
Article
Full-text available
The intent of this research is to generate a set of non-dominated policies from which one of two agents (the leader) can select a most preferred policy to control a dynamic system that is also affected by the control decisions of the other agent (the follower). The problem is described by an infinite horizon, partially observed Markov game (POMG)....
Article
Assuming the probability of an inaccurate state observation is sufficiently small, we present a simple procedure for determining whether a stationary finite-memory controller will improve or degrade system performance, given improved state observation quality. The intent of this result is to lend insight into whether or not to invest in improved st...
Article
Full-text available
We present advances both in modeling and algorithm design for a service network design problem faced by less-than-truckload (LTL) freight transportation carriers. The developed models more accurately capture key operations of today's carriers: decisions for loaded and empty trailer movements are considered simultaneously, and a time dis-cretization...
Article
Ports-of-entry are critical components of the modern international supply chain infrastructure, particularly container seaports and airfreight hubs. The potential operational and economic impact resulting from their temporary closure is unknown but is widely believed to be very significant. This paper investigates one aspect of this potential impac...
Article
This paper presents a computational approach for creating an operational schedule for the tactical load plan used by a less-than-truckload (LTL) motor carrier. A load plan determines how freight is routed through an LTL carrier's linehaul terminal network by specifying a sequence of transfer terminals for all freight shipments, but does not provide...
Article
This paper develops an optimization modeling approach for analyzing the trade-off between the cost of a larger fleet of tractors and the cost of repositioning tractors for a trucking company operating a consolidation network, such as a less-than-truckload (LTL) company. Specifically, we analyze the value of using extra tractor repositioning moves (...
Article
Full-text available
According to the Center for Disease Control approximately 48 million people get sick from foodborne illnesses per year. In 2011, nearly 80% of illnesses were triggered by unspecified agents transmitted through food which highlights the uncertainty about pathogens that are responsible for causing consumers to become ill. This research aims to compar...
Article
In this research we study the berth allocation problem (BAP) in real time as disruptions occur. In practice, the actual arrival times and handling times of the vessels deviate from their expected or estimated values, which can disrupt the original berthing plan and potentially make it infeasible. We consider a given baseline berthing schedule, and...
Article
Dynamic ride-share systems aim to bring together travelers with similar itineraries and time schedules on short-notice. These systems may provide significant societal and environmental benefits by reducing the number of cars used for personal travel and improving the utilization of available seat capacity. Effective and efficient optimization techn...
Article
Quay cranes (QC) are key resources at container terminals, and the efficiency of QC operations is vital for terminal productivity. The Quay Crane Scheduling Problem (QCSP) is to schedule the work activities for a set of cranes assigned to a single berthed vessel with the objective of minimizing the completion time of all container handling tasks. T...
Conference Paper
Our objective is to develop an approach for quantifying the vulnerability of a food product supply chain that may be used by an intelligent adversary to deliver a chemical or biological agent. The approach is intended to create control strategies that seek to ensure a high level of system productivity while mitigating risk. We have developed a supp...
Article
Full-text available
This paper presents solution approaches for a shipper pickup and delivery planning problem to move freight from suppliers to distribution centers. Each shipment is moved either direct via a less-than-truckload (LTL) carrier, or possibly consolidated with other shipments and moved by one or two truckload (FTL) routes. When using a FTL carrier, the s...
Article
Full-text available
Smartphone technology enables dynamic ride-sharing systems that bring together people with similar itineraries and time schedules to share rides on short-notice. This paper considers the problem of matching drivers and riders in this dynamic setting. We develop optimization-based approaches that aim at minimizing the total system-wide vehicle miles...
Article
This paper develops approaches for incorporating informational and operational dynamics within models for intermodal drayage operations with flexible tasks. Tasks with flexible origins or destinations create an important complexity. We develop models to minimize the cost of drayage moves when flexibility exists. The solution approach generates plan...
Conference Paper
Ports play a critical role in transportation infrastructure, but are vulnerable to seismic hazards. Current risk management practices focus on the effect of seismic hazards on individual port structures. However, damage and downtime of these structures has an impact on the overall port system's ship handling operations and the economic impacts that...
Article
This paper defines the Home Health Nurse Routing and Scheduling (HHNRS) problem and presents a rolling horizon approach for its solution. The HHNRS is a dynamic periodic fixed appointment time routing problem with visit time consistency constraints. A set of patients, revealed dynamically, must be visited according to a prescribed weekly frequency...
Article
As critical transportation infrastructure, ports are vulnerable to a variety of natural disasters. On the West Coast of the United States, earthquakes are a concern. Currently, risk management practices for seismic design in ports consider only the seismic performance of individual wharf and crane structures. The practices do not consider how damag...
Article
Full-text available
Time considerations have been largely ignored in the study of vehicle routing problems with stochastic demands, even though they are crucial in practice. We show that tour duration limits can effectively and efficiently be incorporated in solution approaches that build fixed, or a priori, tours for such problems. We do so by assuming that each tour...
Article
Full-text available
Smartphone technology enables dynamic ride-sharing systems that bring together people with similar itineraries and time schedules to share rides on short-notice. This paper considers the problem of matching drivers and riders in this dynamic setting. We develop optimization-based approaches that aim at minimizing the total system-wide vehicle miles...
Article
Full-text available
Ride-share systems, which aim to bring together travelers with similar itineraries and time schedules, may provide significant societal and environmental benefits by reducing the number of cars used for personal travel and improving the utilization of available seat capacity. Effective and efficient optimization technology that matches drivers and...
Article
This article presents a robust branch-cut-and-price algorithm for the heterogeneous fleet vehicle routing problem (HFVRP), vehicles may have distinct capacities and costs. The columns in the formulation are associated to q-routes, a relaxation ...
Article
We propose a practical and flexible fixed routing system that preserves many of the benefits of traditional fixed routes but can be deployed in settings with medium to high variability and delivery time window constraints. The key ideas are the introduction of a new recourse strategy, in which customers are assigned to two planned routes, a primary...
Article
We consider the problem of determining the home locations, or domiciles, of truck drivers for a less-than-truckload carrier. Domiciling decisions are complex, in part due to regulations and union rules restricting driver schedules, but have a significant impact on the operating costs of less-than-truckload carriers. We present an iterative scheme,...
Article
Full-text available
A load plan specifies how freight is routed through a linehaul terminal network operated by a less-than-truckload (LTL) motor carrier. Determining the design of the load plan, a problem of service network design, is critical to effective operations of such carriers. Operations research techniques currently support load plan design, and all models i...
Article
Full-text available
We develop a robust optimization framework for dynamic empty repositioning prob- lems modeled using time-space networks. In such problems, uncertainty arises primar- ily from forecasts of future supplies and demands for assets at different time epochs. The proposed approach models such uncertainty using intervals about nominal fore- cast values and...
Article
This paper describes a scheme for the dynamic management of linehaul drivers developed for a large US less-than-truckload (LTL) carrier. Virtually all scheduling problems faced by transportation service providers are complicated by time-constrained vehicle operators that can be renewed only after resting. LTL driver scheduling is further complicate...
Chapter
Intermodal drayage refers to the local movement of intermodal freight transportation equipment (trailers and containers), both loaded and empty. Drayage service provides the for the vast majority of freight moving via the international intermodal freight chain. For example, a large international import shipper may receive loaded 40-foot ocean conta...
Article
This paper studies the management of a fleet of trucks providing container pickup and delivery service (drayage) to a port with an appointment-based access control system. Responding to growing access congestion and its resultant impacts, many US port terminals have implemented appointment systems, but little is known about the potential impact of...
Article
This paper develops an approach for analyzing how restricting rest (sleep) locations for long-haul truckers may affect operational productivity, given hours-of-service regulations. Productivity is measured by the minimum number of unique drivers required to execute a set of load requests feasibly over a known planning horizon. When drivers may stop...
Article
Full-text available
This paper presents a paired-vehicle recourse strategy for the vehicle routing problem with sto- chastic demands (VRPSD). In the VRPSD, a fleet of homogeneous capacitated vehicles is dispatched from a terminal to serve single-period customer demands which are known in distribution when planning but only revealed with certainty upon vehicle arrival....
Article
Since the terrorist events in the United States on September 11, 2001, the Federal Motor Carrier Safety Administration has been testing and evaluating cargo tracking technologies to improve the safety, security, and efficiency of commercial motor vehicle operations. While satellite-based systems used for tracking vehicles and cargo provide sufficie...
Article
Full-text available
We present a partially observed Markov decision process model of a single product supply chain system with lost sales, in which a single decision maker selects a replenishment quantity at each decision epoch. Demand is modeled using an exogenous Markov chain, such that the distribution of demand in a period is dependent on the demand level in the p...
Article
This paper studies methods for managing a fleet of trucks providing container pickup and de-livery service (drayage) to a port with an appointment-based access control system. Responding to growing access congestion and its resultant impacts, many U.S. port terminals have imple-mented appointment systems, but little is known about the impact of suc...