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Rebalancing Integrated, Demand-Responsive Passenger and Freight Transport – An Agent-Based Simulation Approach
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Ride‐hailing services have the potential to play a major role within future transport systems. While the operation as well as environmental, social and economic consequences are research subjects, the focus in the literature lies on system efficiency and profitability. In this study, vehicle relocation strategies are investigated with respect to service provision equity using an agent‐based simulation approach. The aim is to identify ways of operation that support social fairness while maintaining the profitability and effectiveness of the service. The results show that a typical demand‐anticipatory relocation strategy leads to an imbalance in the spatial distribution of mean wait times for the use case of Berlin. This can be significantly improved by applying different relocation strategies. As a consequence, the overall demand for the system rises while the ratio of empty vehicle kilometres increases slightly.
Serving both passenger and freight demand with the same vehicle fleet is an ambition that led to the development of several innovative vehicle concepts [10, 26]. This study proposes a simulation-based methodology to investigate the execution of freight tours with an On-Demand fleet of autonomous, modular vehicles while giving priority to passenger transport. Based on assumptions regarding the operational scheme, tour pricing and delivery time windows, the software Multi-Agent Transport Simulation (MATSim) is extended. The developed methodology is then applied to a Berlin-wide freight delivery scenario. The results show that when using a relatively large vehicle fleet, passenger waiting time statistics barely change. However, it has to be noted that the study should be repeated with different (smaller) fleet sizes. A rough cost analysis for the freight operator suggests that there is a large saving potential when using autonomous On-Demand vehicles instead of an owned fleet. Because of the uncertainty of price composition, further studies to quantify this saving potential have to be made.
Background
Despite emerging research on novel mobility solutions in urban areas, there have been few attempts to explore the relevance and sustainability of these solutions in rural contexts. Furthermore, existing research addressing rural mobility solutions typically focuses on a specific user group, such as local residents, second-home owners, or tourists. In this paper, we study the social inclusivity, economic viability, and environmental impacts of novel mobility solutions in rural contexts based on published scholarly literature. When doing so, we bring both permanent and temporary residents of rural areas under one research framework.
Methods
We used grey literature to identify and categorise novel mobility solutions, which have been applied in European rural areas and are suitable for travelling longer distances. By using six service flexibility variables, we reached four categories of novel mobility solutions: semi-flexible demand-responsive transport, flexible door-to-door demand-responsive transport, car-sharing, and ride-sharing. We analysed the social inclusivity, economic viability, and environmental impacts of those categories based on criteria and evidence identified from scholarly literature by including the perspectives of both permanent and temporary residents of rural areas. Conclusion: Integration of the needs of various user groups is essential when aiming to achieve the provision of environmentally, socially, and economically sustainable mobility solutions in rural areas.
Results
Our findings revealed that while single novel mobility solutions are seldom applicable for all rural travellers, strong spatial and temporal synergies exist when combining different solutions. The need for a connected and flexible set of mobility solutions sensitive to the temporal and spatial patterns of mobility needs is inevitable. Accessible and easily understandable information on routing, booking, and ticketing systems, as well as cooperation, shared values, and trust between various parties, are key success factors for sustainable rural mobility.
Conclusion
Integration of the needs of various user groups is essential when aiming to achieve the provision of environmentally, socially, and economically sustainable mobility solutions in rural areas.
Time-sensitive parcel deliveries—shipments requested for delivery in a day or less—are an increasingly important aspect of urban logistics. It is challenging to deal with these deliveries from a carrier perspective. These require additional planning constraints, preventing the efficient consolidation of deliveries that is possible when demand is well known in advance. Furthermore, such time-sensitive deliveries are requested to a wider spatial scope than retail centers, including homes and offices. Therefore, an increase in such deliveries is considered to exacerbate negative externalities, such as congestion and emissions. One of the solutions is to leverage spare capacity in passenger transport modes. This concept is often denominated as cargo hitching. While there are various system designs, it is crucial that such a solution does not deteriorate the quality of service of passenger trips. This research aims to evaluate the use of mobility-on-demand (MOD) services that perform same-day parcel deliveries. To test the MOD-based solutions, we utilize a high-resolution agent- and activity-based simulation platform of passenger and freight flows. E-commerce demand carrier data collected in Singapore are used to characterize simulated parcel delivery demand. We explore operational scenarios that aim to minimize the adverse effects of fulfilling deliveries with MOD service vehicles on passenger flows. Adverse effects are measured in fulfillment, wait, and travel times. A case study on Singapore indicates that the MOD services have potential to fulfill a considerable amount of parcel deliveries and decrease freight vehicle traffic and total vehicle kilometers travelled without compromising the quality of MOD for passenger travel. Insights into the operational performance of the cargo-hitching service are also provided.
Ride- Parcel- Pooling expands conventional ride-pooling on-demand mobility services. It does not only offer passengers shared rides but also integrates parcels into the assignment problem to increase vehicle utilization during times of low passenger demand. This article examines the potential behind the combination of on-demand mobility and city logistics using a case study for the city of Munich, Germany. We examined and evaluated the effects of Ride-Parcel-Pooling in three different scenarios. The first scenario replicates the status quo (two separate services for passenger and parcel delivery), while scenarios two and three examine different forms of combining on-demand mobility and city logistics. This study shows that about 80 % of the distance traveled to provide logistics services could be saved. Within the case study, this work also provides insights on the environmental impacts of Ride-Parcel-Pooling by analyzing the most prominent global and local emission parameters of road traffic. Results show a reduction of overall CO 2 emissions as well as of the investigated local air pollutants NOx, PM 10 , CO, and SO 2 .
The shared autonomous vehicle (SAV) is a new concept that meets the upcoming trends of autonomous driving and changing demands in urban transportation. SAVs can carry passengers and parcels simultaneously, making use of dedicated passenger and parcel modules on board. A fleet of SAVs could partly take over private transport, taxi, and last-mile delivery services. A reduced fleet size compared to conventional transportation modes would lead to less traffic congestion in urban centres. This paper presents a method to estimate the optimal capacity for the passenger and parcel compartments of SAVs. The problem is presented as a vehicle routing problem and is named variable capacity share-a-ride-problem (VCSARP). The model has a MILP formulation and is solved using a commercial solver. It seeks to create the optimal routing schedule between a randomly generated set of pick-up and drop-off requests of passengers and parcels. The objective function aims to minimize the total energy costs of each schedule, which is a trade-off between travelled distance and vehicle capacity. Different scenarios are composed by altering parameters, representing travel demand at different times of the day. The model results show the optimized cost of each simulation along with associated routes and vehicle capacities.
Transport can play a key role in mitigating climate change, through reducing traffic, emissions and dependency on private vehicles. Transport is also crucial to connect remote areas to central or urban areas. Yet, sustainable and flexible transport is among the greatest challenges for rural areas and rural–urban regions. Innovative transport concepts and approaches are urgently needed to foster sustainable and integrated regional development. This article addresses challenges of sustainability, accessibility, and connectivity through examining complementary systems to existing public transport, including demand-responsive transport and multimodal mobility. We draw upon case studies from the Metropolitan Area of Styria, Ljubljana Urban Region and rural Wales (GUSTmobil, REGIOtim, EURBAN, Bicikelj, Bwcabus, Grass Routes). In-depth analysis through a mixed-methods case study design captures the complexity behind these chosen examples, which form a basis for analysing the effects of services on accessibility for different groups, connectivity to public transport and usability as a “first and last mile” feeder. We further explore the weaknesses of complementary transport systems, including legal, organisational and financial barriers, and offer potential solutions to structure and communicate complementary transport systems to improve access and use. Looking ahead, we use the case studies to anticipate innovative, sustainable “mobility as a service” (MaaS) solutions within and between urban and rural areas and consider how future public policy orientations and arrangements can enable positive change. A main concern of our article and the contribution to scientific literature is through exploring the benefit of well-established multi-level governance arrangements when introducing smaller-scale mobility solutions to improve rural–urban accessibility. It becomes clear that not a one-size-fits-all model but placed-based and tailored approaches lead to successful and sustainable concepts.
With shared mobility services becoming increasingly popular and vehicle automation technology advancing fast, there is an increasing interest in analysing the impacts of large-scale deployment of shared automated vehicles. In this study, a large fleet of shared automated vehicles providing private rides to passengers is introduced to an agent-based simulation model based on the city of Amsterdam, the Netherlands. The fleet is dimensioned for a sufficient service efficiency during peak-hours, meaning that in off-peak hours a substantial share of vehicles is idle, requiring vehicle relocation strategies. This study assesses the performance of zonal pro-active relocation strategies for on-demand passenger transport under constrained curbside parking capacity: (1) demand-anticipation, (2) even supply dispersion and (3) balancing between demand and supply of vehicles. The strategies are analysed in regard to service efficiency (passenger waiting times, operational efficiency), service externalities (driven mileage, parking usage) and service equity (spatial distribution of externalities and service provision). All pro-active relocation strategies are outperformed by a naïve remain-at-drop off-location strategy in a scenario where curbside parking capacity is in abundance. The demand-anticipation heuristic leads to the highest average waiting times due to vehicle bunching at demand-hotspots which results in an uneven usage of parking facilities. The most favourable results in regard to service efficiency and equity are achieved with the heuristics balancing demand and supply, at the costs of higher driven mileage due to the relocation of idle vehicles. These results open up opportunities for municipalities to accompany the introduction of large fleets of shared automated vehicles with suitable curbside management strategies that mitigate undesired effects.
Worldwide, ridesharing business is steadily growing and has started to receive attention also by public transport operators. With future fleets of Autonomous Vehicles, new business models connecting schedule-based public transport and feeder fleets might become a feasible transport mode. However, such fleets require a good management to warrant a high level of service. One of the key aspects of this is proactive vehicle rebalancing based on the expected demand for trips. In this paper we model vehicle rebalancing as the Dynamic Transportation Problem. Results suggest that waiting times can be cut by around 30 % without increasing the overall vehicle miles travelled for a feeder fleet in rural Switzerland.
ABSTRACT
Demand Responsive Transport (DRT) offers a collective flexible travel alternative that can potentially complement Fixed Transit (FT). The combination of an on-demand and line-based services holds the promise of improved mobility and increased service coverage. However, insofar it remains unknown whether DRT services deliver such much anticipated improvements. This study presents an assessment framework to evaluate the performance of DRT and related changes in accessibility and performs an empirical analysis for a recently introduced DRT service in the Netherlands. The framework includes a performance benchmark between DRT and FT based on the computation of generalized journey times of the DRT rides and the FT alternatives, and it can help identify whether DRT is used as complement or substitute of FT. The framework covers the spatial and temporal dimensions, and the explicit consideration of rejected trips is an integral part of the evaluation. Results suggest large accessibility improvements for DRT users, especially for some underserved origin-destination pairs.
Significance
Ride-sharing services can provide not only a very personalized mobility experience but also ensure efficiency and sustainability via large-scale ride pooling. Large-scale ride-sharing requires mathematical models and algorithms that can match large groups of riders to a fleet of shared vehicles in real time, a task not fully addressed by current solutions. We present a highly scalable anytime optimal algorithm and experimentally validate its performance using New York City taxi data and a shared vehicle fleet with passenger capacities of up to ten. Our results show that 2,000 vehicles (15% of the taxi fleet) of capacity 10 or 3,000 of capacity 4 can serve 98% of the demand within a mean waiting time of 2.8 min and mean trip delay of 3.5 min.
The synchronized last mile logistics concept seeks to address, through coordinated collaboration, several challenges that hinder reliability, cost efficiency, effective resource planning, scheduling and utilization; and increasingly, sustainability objectives. Subsequently, the meeting of service level and contractual commitments are competitively impacted with any loss of efficiency. These challenges, against a backdrop of Singapore, can essentially be addressed in selected industry sectors through a better understanding of logistics structures; innovative supply chain designs and coordination of services, operations and processes coupled with concerted policies and supply chain strategies. (C) 2014 The Authors. Published by Elsevier Ltd.
This article is concerned with how to conceptualize and theorize the nature of the ‘car system’ that is a particularly key, if surprisingly neglected, element in ‘globalization’. The article deploys the notion of systems as self-reproducing or autopoietic. This notion is used to understand the origins of the 20th-century car system and especially how its awesome pattern of path dependency was established and exerted a particularly powerful and self-expanding pattern of domination across the globe. The article further considers whether and how the 20th-century car system may be transcended. It elaborates a number of small changes that are now occurring in various test sites, factories, ITC sites, cities and societies. The article briefly considers whether these small changes may in their contingent ordering end this current car system. The article assesses whether such a new system could emerge well before the end of this century, whether in other words some small changes now may produce the very large effect of a new post-car system that would have great implications for urban life, for mobility and for limiting projected climate change.
In pickup and delivery problems vehicles have to transport loads from origins to destinations without transshipment at intermediate locations. In this paper, we discuss several characteristics that distinguish them from standard vehicle routing problems and present a survey of the problem types and solution methods found in the literature.
Understanding the nature of transit dwell time has potential benefits for both users and operators. In this article, multiple regression models are estimated to analyse the influence of different payment methods, the existence of steps at doors, the age of passengers and the possible friction between users boarding, alighting and standing, on explaining observed variation in dwell times. Using the estimated boarding and alighting average times, performance comparisons are simulated assuming a service with payment outside buses, a prepaid card validated inside buses and cash transactions. Results show the specific effect of all the variables involved in determining the bus dwell time at stops, in particular, that substantial time savings are accruable if payment methods are upgraded from slow techniques, such as cash transactions to the fastest one (fare paid outside buses) while intermediate technologies such as prepaid cards validated inside buses (with or without contact) fall in between. On the other hand, the existence of two steps at the front door makes the boarding process slower, and senior passengers are slower to board and alight than younger travellers. A friction effect was also found when passengers boarding form two queues through a single door, which increases the boarding time for one of the queues; and a crowding effect, as the presence of passengers standing inside the bus slightly slows both boarding and alighting.
The paper presents radical new urban transportation system concepts, potentially allowing changing the economic and environmental costs of passenger and freight transportation. The driver focuses on the concept of sharing, which means to make a joint use of transport resources, between passengers and goods flows. From a field observation of several existing solutions, an inductive reasoning enables us to move from a set of specific facts to establish an archetype for a radical new urban transportation system. Once the archetype defined, it is translated in real life through the example of the On Route proposal for London. The research frame of this paper is the ANR C-Goods (City Goods Operation Optimization using Decision support System) project. Started in February 2009 the project involves four partners , and will end on 2011.
We consider the Vehicle Routing Problem, in which a fixed fleet of delivery vehicles of uniform capacity must service known
customer demands for a single commodity from a common depot at minimum transit cost. This difficult combinatorial problem
contains both the Bin Packing Problem and the Traveling Salesman Problem (TSP) as special cases and conceptually lies at the
intersection of these two well-studied problems. The capacity constraints of the integer programming formulation of this routing
model provide the link between the underlying routing and packing structures. We describe a decomposition-based separation
methodology for the capacity constraints that takes advantage of our ability to solve small instances of the TSP efficiently.
Specifically, when standard procedures fail to separate a candidate point, we attempt to decompose it into a convex combination
of TSP tours; if successful, the tours present in this decomposition are examined for violated capacity constraints; if not,
the Farkas Theorem provides a hyperplane separating the point from the TSP polytope. We present some extensions of this basic
concept and a general framework within which it can be applied to other combinatorial models. Computational results are given
for an implementation within the parallel branch, cut, and price framework SYMPHONY.
This paper examines the integration of freight delivery into the passenger transport of an on-demand ride-pooling service. The goal of this research is to use existing passenger trips for logistics services and thus reduce additional vehicle kilometers for freight delivery and the total number of vehicles on the road network. This is achieved by merging the need for two separate fleets into a single one by combining the services. This research provides an extensive literature review and discusses policy measures supporting such a service. To evaluate the potential of such a mobility-on-demand service, this paper uses an agent-based simulation framework and integrates three heuristic parcel assignment strategies into a ride-pooling fleet control algorithm. Two integration scenarios (moderate and full) are set up. While in both scenarios passengers and parcels share rides in one vehicle, in the moderate scenario no stops for parcel pick-up and delivery are allowed during a passenger ride to decrease customer inconvenience. Using real-world demand data for a case study of Munich, Germany, the two integration scenarios together with the three assignment strategies are compared to the status quo, which uses two separate vehicle fleets for passenger and logistics transport. The results indicate that the integration of logistics services into a ride-pooling service is possible and can exploit unused system capacities without deteriorating passenger transportation. Depending on the assignment strategies nearly all parcels can be served until a parcel to passenger demand ratio of 1:10 while the overall fleet kilometers can be decreased compared to the status quo.
Environmental sustainability is among the key concerns of our time. Especially the traffic and transportation sector entails a high degree of negative consequences on sustainability metrics such as CO2 emissions, increasing the need for innovative concepts to cope with the requirements of our modern society, while at the same decreasing environmental pollution. A potential solution in this regard are grocery deliveries (e-grocery), which can achieve economies of scale by bundling multiple orders. Within the last two decades, multiple e-grocery concepts have evolved in operational practice, which we asses by means of a comprehensive simulation study, to guide future systematic investigation on (simulation-based) sustainability research. The concrete results of our study indicate that grocery deliveries by courier, express and parcel (CEP) organizations can outperform fulfillment strategies based on insourcing by up to 50% in terms of mileages as well as 39% and 66% regarding CO2 and PM2.5 emissions.
The integration of passenger and freight transport has been the subject of debate among scholars from the beginning of the century, with a peak observed in the last five years. Considering the relatively recent interest in the topic, most authors have highlighted the heterogeneous and explorative approaches adopted so far, indicating a lack of systematic analyses. This is confirmed by the different names given to the same concept (e.g., co-modality, cargo hitching, system with mixed passengers and goods, share-a-ride, integrated passenger and freight logistics, and collaborative passenger and freight transport). This study conducts a comprehensive literature review based on the scientific contributions indexed in Scopus and selected through a semiautomatic data extraction. First, a descriptive analysis is conducted, which includes types of publication, geographical areas, sources of publication, research methods, and research design adopted. Then, a text mining analysis identifies the main content-related aspects, including a semantic investigation of the most frequently occurring terms, their clustering in homogeneous groups, the transport means considered, and the territorial scales that have been investigated. This analysis is used to define the future challenges related to the topic, which span from the provision of more robust quantitative analyses (studies providing real data and adopting ad-hoc models are still very limited) to policy-related issues. However, the definition of a normative framework that integrates both systems is essential to deal with passenger–freight transport in a combined manner.
This paper explores the potential integration of freight transport into a Mobility as a Service (MaaS) environment. MaaS is a user-oriented service concept providing door-to-door mobility solutions for people. It integrates services of multiple providers, enabling searching, booking, and payment through a single digital platform. Although MaaS is often presented as a great opportunity to increase the efficiency of the overall transport system, its application is constrained to passenger transport. The possibility of combining freight and passenger trips in MaaS might contribute to improving capacity utilization in passenger transport and to reducing freight movements in cities. The aim of the paper is to systematically explore the service models through which integration might take place and to qualitatively assess their potential impact. Based on a suitable conceptualization of MaaS, we identify relevant logistics segments, propose service models and evaluate these from a multi-stakeholder and sustainability perspective. The analysis results in propositions about the fitness between on-demand freight and passenger systems combined in MaaS, as well as a related research agenda to further investigate the potential of this approach for future sustainable mobility.
The “First-Last Mile” problem (FLM) is a relevant transport issue. According to the Green Paper on Urban Mobility, the combination of passenger and freight flows may be a valid approach to promote sustainable, efficient and socially desirable FLM transport. This paper proposes a set of key performance indicators to evaluate potential improvements in operational, environmental and social performances of integrated passenger and freight flows, compared to the current transport schemes. The two case studies of the Northern lagoon of Venice in Italy and the Slovenian Municipality of Velenje indicate that the model may be particularly effective in those cases where reduced freight volumes, limited freight pickup/delivery locations and a lower elasticity of the travel demand reduce the constraints to the adoption of this integrated scheme. Results call for a reduction both in distances travelled and in externalities produced, and hence a good potential in FLM terms. Beside these technical aspects, one of the main issues is the need for innovation in the normative/regulatory context: a prerequisite in order to apply this solution to real-life contexts.
Mobility is fundamentally important in enabling people to access services, which can deliver substantial benefits to people's quality of life. This is particularly important in rural areas where the range and extent of public transport services are, in general, significantly lower than in urban areas, and, indeed, below the level required to provide a level of service that is sufficiently high to enable people in rural areas without private cars to access these services. This paper looks at the role of governments in institutional, organisational, regulatory and financial frameworks in supporting rural transport services at a level that enables this access. A cluster analysis is performed to identify distinct classes of framework types across Europe. In addition, the paper gives examples of good practice and innovation in rural transport from across Europe incorporating a variety of themes: the use of Information and Communications Technology, intermodal service coordination, demand-responsive transport, shared mobility and good governance. Key success factors for introducing, sustaining and transferring these forms of good practice are then discussed.
Mobility-on-demand (MoD) services are provided by multiple competing companies. In their competition for travelers, they need to provide minimum travel costs, or travelers will switch to competitors. This study developed a dynamic traffic assignment of MoD systems. A static traffic assignment (STA) model is first defined. When demand is asymmetric, empty rebalancing trips are required to move vehicles to traveler origins, and the optimal rebalancing flows are found by a linear program. Because of the time-dependent nature of traveler demand, the model was converted to dynamic traffic assignment (DTA). The method of successive averages, which is provably convergent for STA, was used to find dynamic user equilibrium (DUE). The simulation was conducted on two networks. The MoD system was simulated with different fleet sizes and demands. The results showed that the average total delay and travel distance decreased with the increase in fleet size whereas the average on-road travel time increased with the fleet size. The result of traffic assignment of one network with MoD system was compared with a network where all travelers use private vehicles. The results showed that the network with MoD system created more trips but less traffic congestion. © National Academy of Sciences: Transportation Research Board 2019.
Die Untersuchung dynamischer Sachverhalte wird in vielen Bereichen der Ingenieur-, Natur- und Wirtschaftswissenschaften über die Methodik der Simulation unterstützt. Auch in der Logistik hat die Simulation zur methodischen Absicherung der Planung, Steuerung und Überwachung der Material-, Personen-, Energie- und Informationsflüsse seit Jahren ihren berechtigten Stellenwert. Daher wird die Notwendigkeit des Einsatzes der Simulation zur Planung, Realisierung und Betriebsführung logistischer Systeme heute nicht mehr in Frage gestellt. Der Beitrag gibt einen umfassenden Einstieg in die Simulationsthematik im Bereich der Logistik.
“First and Last Mile Delivery” stands for freight transport logistics over the first and the last part of the way to the customer, accordingly. In freight transport, the first and the last mile are most cost intensive. In the last phase of transport, it is difficult to gather and put shipments together, which results in the costs in that area usually being disproportionately high. The problems of last mile delivery usually stem from the fact that deliveries are composed of individual orders and from a significant level of dispersal of destinations, as each order must be delivered to a different address. Similar problems are related to first mile freight transport. This article addresses the problems and issues connected with first and last mile delivery.
This article investigates the potential of integrating a shared goods and passengers on-demand rapid transit system in urban areas. Although persons and goods movements have different objectives and constraints, mixing their travels on the same network is within current trends. So we investigate in this paper how they could share a rapid transit network and use the available transportation capacity within a city more efficiently in an interconnected way. Based on the common characteristics of personal rapid transit (PRT) and freight rapid transit (FRT), this paper proposes an emergent and efficient transportation solution in order to enhance the sustainability of city logistics. Next, the operational level is focused on to characterize the dynamic transportation problem and to propose two strategies to formulate it. This problem aims to respond to the number of transportation requests arriving on a periodic basis with adequate service level while minimizing the empty movements of a set of electric vehicles with limited battery capacity. An efficient solution approach based on the forward optimization of periodic transportation sub-problems is proposed and validated. The applicability of the PRT-FRT mode is demonstrated and computational results in comparison to other transportation option is also presented and discussed.
Carsharing programs that operate as short-term vehicle rentals (often for one-way trips before ending the rental) like Car2Go and ZipCar have quickly expanded, with the number of US users doubling every 1–2 years over the past decade. Such programs seek to shift personal transportation choices from an owned asset to a service used on demand. The advent of autonomous or fully self-driving vehicles will address many current carsharing barriers, including users’ travel to access available vehicles.This work describes the design of an agent-based model for shared autonomous vehicle (SAV) operations, the results of many case-study applications using this model, and the estimated environmental benefits of such settings, versus conventional vehicle ownership and use. The model operates by generating trips throughout a grid-based urban area, with each trip assigned an origin, destination and departure time, to mimic realistic travel profiles. A preliminary model run estimates the SAV fleet size required to reasonably service all trips, also using a variety of vehicle relocation strategies that seek to minimize future traveler wait times. Next, the model is run over one-hundred days, with driverless vehicles ferrying travelers from one destination to the next. During each 5-min interval, some unused SAVs relocate, attempting to shorten wait times for next-period travelers.Case studies vary trip generation rates, trip distribution patterns, network congestion levels, service area size, vehicle relocation strategies, and fleet size. Preliminary results indicate that each SAV can replace around eleven conventional vehicles, but adds up to 10% more travel distance than comparable non-SAV trips, resulting in overall beneficial emissions impacts, once fleet-efficiency changes and embodied versus in-use emissions are assessed.
In this paper we review the exact algorithms based on the branch and bound approach proposed in the last years for the solution of the basic version of the vehicle routing problem (VRP), where only the vehicle capacity constraints are considered. These algorithms have considerably increased the size of VRPs that can be solved with respect to earlier approaches. Moreover, at least for the case in which the cost matrix is asymmetric, branch and bound algorithms still represent the state-of-the-art with respect to the exact solution. Computational results comparing the performance of different relaxations and algorithms on a set of benchmark instances are presented. We conclude by examining possible future directions of research in this field.
“Cities, Mobility and Climate Change”
- D Banister
Shared-Vehicle Mobility-on-Demand Systems: A Fleet Operator's Guide to Rebalancing Empty Vehicles
- K Spieser
- S Samaranayake
- W Gruel
- E Frazzoli
Shared-Vehicle Mobility-on-Demand Systems: A Fleet Operators Guide to Rebalancing Empty Vehicles
- Spieser