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Hongqi Li
School of Transportation Science and Engineering, Beihang University. No. 37 Xueyuan Road, Haidian District, Beijing, 100191, China

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Review
Published: 15 February 2021 in European Journal of Operational Research
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More and more studies have aimed to optimize the ground vehicle (GV) and unmanned aerial vehicle (UAV) system in which GVs function as mobile satellites and UAVs are dispatched from GVs for last-mile deliveries. From the two-echelon scheme perspective, GV routes originating at the depot are on one echelon, and UAV routes originating at satellites are on the other echelon. A change in a GV route may affect some UAV routes, which indicates the satellite synchronization. In the past decade, the optimization of vehicle routes in two-echelon networks has attracted increasing attention in the operations research community. We classify routing problems of two-echelon networks based on the modeling mechanism connecting the two echelons. Different formulations for describing connection mechanisms of the two-echelon scheme, especially constraints on capacitated satellites, satellite synchronization, vehicle coupling/decoupling at satellites, etc., are briefly introduced. There are several modeling challenges of optimizing delivery routes for a fleet of GV–UAV combinations that include new connection mechanisms between the two echelons. Some important variants, especially those involving mobile satellite synchronization, and GV–UAV flexibly coupling/decoupling, require new mathematical formulations and algorithms catering to more general and practical situations.

ACS Style

Hongqi Li; Jun Chen; Feilong Wang; Ming Bai. Ground-vehicle and unmanned-aerial-vehicle routing problems from two-echelon scheme perspective: A review. European Journal of Operational Research 2021, 294, 1078 -1095.

AMA Style

Hongqi Li, Jun Chen, Feilong Wang, Ming Bai. Ground-vehicle and unmanned-aerial-vehicle routing problems from two-echelon scheme perspective: A review. European Journal of Operational Research. 2021; 294 (3):1078-1095.

Chicago/Turabian Style

Hongqi Li; Jun Chen; Feilong Wang; Ming Bai. 2021. "Ground-vehicle and unmanned-aerial-vehicle routing problems from two-echelon scheme perspective: A review." European Journal of Operational Research 294, no. 3: 1078-1095.

Journal article
Published: 05 August 2020 in Research in Transportation Business & Management
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The coordinated operation of intercity linehaul that relies on high-speed trains and urban transportation modes is important and necessary to maintain the service level of passenger transportation. To improve the performance of the high-speed railway station operation, this paper introduces the feeder-vehicle routing and high-speed-train assignment problem with time windows (FVRTAP-TW). The FVRTAP-TW objective is to minimize the average of passengers' delaying time at the high-speed railway station through optimizing feeder-vehicle routes and passengers' assignments to high-speed trains. The FVRTAP-TW has the characters of time windows, assignment decisions on the connection between urban transport and intercity linehaul, and heterogeneous fleets. We define the FVRTAP-TW and develop a mathematical model. An adaptive large neighborhood search (ALNS) algorithm is proposed. Computational experiments are conducted to test the model and the ALNS algorithm. Computational results indicate that it is practicable and necessary to improve the service level of the high-speed railway station and the passenger experiences by considering the interaction of urban-transport routes and the schedule high-speed trains.

ACS Style

Hongqi Li; Jun Chen; Shaokai He. The feeder-vehicle routing and high-speed-train assignment problem with time windows. Research in Transportation Business & Management 2020, 38, 100521 .

AMA Style

Hongqi Li, Jun Chen, Shaokai He. The feeder-vehicle routing and high-speed-train assignment problem with time windows. Research in Transportation Business & Management. 2020; 38 ():100521.

Chicago/Turabian Style

Hongqi Li; Jun Chen; Shaokai He. 2020. "The feeder-vehicle routing and high-speed-train assignment problem with time windows." Research in Transportation Business & Management 38, no. : 100521.

Journal article
Published: 24 June 2020 in European Journal of Operational Research
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In considering route optimization at a series of express stages from pickup to delivery via the intercity linehaul, we introduce the two-echelon vehicle routing problem with satellite bi-synchronization (2E-VRP-SBS) from the perspective of modeling the routing problems of two-echelon networks. The 2E-VRP-SBS involves the inter-satellite linehaul on the first echelon, and the pickups from senders to origin satellites (i.e., satellites for cargo collection) and deliveries from destination satellites (i.e., satellites for cargo deliveries) to receivers on the second echelon. The 2E-VRP-SBS integrates satellite bi-synchronization constraints, multiple vehicles, and time window constraints on the two-echelon network and aims to find cost-minimizing routes for various types of trucks. Satellite bi-synchronization constraints, which synchronously guarantee the synchronization at origin satellites and the synchronization at destination satellites, provide an innovative method to formulate the two-echelon routing problem. In this study, we develop a mixed-integer programming model for the 2E-VRP-SBS. An exact method using CPLEX solver is presented and a modified adaptive large neighborhood search is conducted. Furthermore, the effectiveness of the 2E-VRP-SBS formulation and the applicability of the heuristic for various instances are experimentally evaluated.

ACS Style

Hongqi Li; Haotian Wang; Jun Chen; Ming Bai. Two-echelon vehicle routing problem with satellite bi-synchronization. European Journal of Operational Research 2020, 288, 775 -793.

AMA Style

Hongqi Li, Haotian Wang, Jun Chen, Ming Bai. Two-echelon vehicle routing problem with satellite bi-synchronization. European Journal of Operational Research. 2020; 288 (3):775-793.

Chicago/Turabian Style

Hongqi Li; Haotian Wang; Jun Chen; Ming Bai. 2020. "Two-echelon vehicle routing problem with satellite bi-synchronization." European Journal of Operational Research 288, no. 3: 775-793.

Journal article
Published: 10 June 2020 in Transportation Research Part B: Methodological
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To tackle the logistics challenges faced by enterprises using unmanned aerial vehicles (UAV) with human-driven vans for parcel deliveries, we introduce the two-echelon vehicle routing problem with time windows and mobile satellites (2E-VRP-TM), which, when solved, optimizes delivery routes for a fleet of van-UAV combinations. Typically, one van carries several UAVs. The first echelon involves time-window-driven parcel deliveries using vans from a distribution center (DC) to customers. The second echelon involves UAVs being dispatched from mobile-satellite vans to serve customers with time windows and directly delivering parcels from the DC. When the first-echelon vehicles park at customer locations and wait for second-echelon vehicle departures and returns, the first-echelon vehicles are used as mobile satellites. We develop a vehicle-flow formulation, in which the mobile-satellite synchronization constraints are included to ensure the echelon interaction. We provide an adaptive large neighborhood search heuristic. Computational experiments evaluate the validity of the 2E-VRP-TM formulation and the effectiveness of the heuristic.

ACS Style

Hongqi Li; Haotian Wang; Jun Chen; Ming Bai. Two-echelon vehicle routing problem with time windows and mobile satellites. Transportation Research Part B: Methodological 2020, 138, 179 -201.

AMA Style

Hongqi Li, Haotian Wang, Jun Chen, Ming Bai. Two-echelon vehicle routing problem with time windows and mobile satellites. Transportation Research Part B: Methodological. 2020; 138 ():179-201.

Chicago/Turabian Style

Hongqi Li; Haotian Wang; Jun Chen; Ming Bai. 2020. "Two-echelon vehicle routing problem with time windows and mobile satellites." Transportation Research Part B: Methodological 138, no. : 179-201.

Journal article
Published: 21 December 2018 in Sustainability
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China’s air transportation system is evolving with its own unique mechanism. In particular, the structural features of the Chinese air passenger network (CAPN) are of interest. This paper aims to analyze the CAPN from holistic and microcosmic perspectives. Considering that the topological structure and the capacity (i.e., available passenger-seats) flow are important to the air network’s performance, the CAPN structure features from non-weighted and weighted perspectives are analyzed. Subnets extracted by time-scale constraints of one day or every two-hours are used to find the temporal features. This paper provides some valuable conclusions about the structural characteristics and temporal features of the CAPN. The results indicate that the CAPN has a small-world and scale-free structure. The cumulative degree distribution of the CAPN follows a two-regime power-law distribution. The CAPN tends to be disassortative. Some important airports, including national air-hubs and local air-hubs, remarkably affect the CAPN. About 90% of large capacities exist between airports with large degrees. The properties of CAPN subnets extracted by taking two hours as the time-scale interval shed light on the air network performance and the changing rule more accurately and microcosmically. The method of the spectral destiny estimation is used to find the implicit periodicity mathematically. For most indicators, a one-day cycle, two-day cycle, and/or three-day cycle can be found.

ACS Style

Hongqi Li; Haotian Wang; Ming Bai; Bin Duan. The Structure and Periodicity of the Chinese Air Passenger Network. Sustainability 2018, 11, 54 .

AMA Style

Hongqi Li, Haotian Wang, Ming Bai, Bin Duan. The Structure and Periodicity of the Chinese Air Passenger Network. Sustainability. 2018; 11 (1):54.

Chicago/Turabian Style

Hongqi Li; Haotian Wang; Ming Bai; Bin Duan. 2018. "The Structure and Periodicity of the Chinese Air Passenger Network." Sustainability 11, no. 1: 54.

Journal article
Published: 08 December 2018 in Computers & Industrial Engineering
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In the two-echelon city logistics system, satellites enable cargo transshipment. Considering on-street satellite phenomena in city logistics practices and the concept of road space sharing between delivery operations and city traffic, we introduce the two-echelon city logistics system with on-street satellites (2E-CLS-OS). The 2E-CLS-OS uses time windows and satellite transshipment constraints to make routes of each of the two echelons interacting. At various time windows of on-street satellites, the real-time transshipment capacity needed by the transshipment operation is constrained by the permitted maximal transshipment capacity and the occupied transshipment capacity. The mathematical formulation for the 2E-CLS-OS is developed. The variable neighborhood search (VNS) heuristic is provided, based on the initial solution constructed by the savings-based heuristic (CW). The model formulation and the VNS are tested by using 20 randomly-generated small-scale instances. The VNS is used to solve 33 realistic instances with up to 30 on-street satellites and 900 customers. The economic difference between the electric vehicles and diesel ones on the second echelon and the impact of varying the truck capacity and the electric tricycle capacity are experimentally analyzed.

ACS Style

Hongqi Li; Yinying Liu; Kaihang Chen; Qingfeng Lin. The two-echelon city logistics system with on-street satellites. Computers & Industrial Engineering 2018, 139, 105577 .

AMA Style

Hongqi Li, Yinying Liu, Kaihang Chen, Qingfeng Lin. The two-echelon city logistics system with on-street satellites. Computers & Industrial Engineering. 2018; 139 ():105577.

Chicago/Turabian Style

Hongqi Li; Yinying Liu; Kaihang Chen; Qingfeng Lin. 2018. "The two-echelon city logistics system with on-street satellites." Computers & Industrial Engineering 139, no. : 105577.

Journal article
Published: 01 July 2018 in Transportation Research Part B: Methodological
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Taking the waste collection management as the practical background, the rollon-rolloff vehicle routing problem (RRVRP) involves tractors pulling large containers between customer locations and the disposal facility. Each used-tractor begins and ends its route at the depot. Customer demand includes emptying a full container, ordering an empty container or changing a container. The objective is to find tractor routes that feature the minimum amount of total nonproductive time. In the literature the RRVRP is formulated as the node routing problem, and the “trip” definition that is the complete transport service of a container is used. To relax some assumptions of the RRVRP to cater to practical desires, we present a variant called the generalized RRVRP (G-RRVRP). The G-RRVRP generalizes the practical background, the objective function and the demand flow, and considers specially container loading and unloading time constraints. The G-RRVRP classifies demand into loaded-container demand and cargo demand with time windows. On condition of respecting container loading/unloading time and customer time windows, the G-RRVRP can design tractor routes for the synchronous scheduling of loaded and empty containers so as to ensure the timeliness of transport service. The G-RRVRP aims to minimize the total running cost of used tractors, instead of the total nonproductive time of tractors adopted by the RRVRP. A mixed integer linear programming model for the G-RRVRP is proposed. The Benders decomposition algorithm involving Pareto-optimal cuts and Benders decomposition-callback implementation, and a two-stage heuristic involving the savings algorithm followed by a local search phase are provided. The mathematical formulation and the two-stage heuristic are tested by solving 40 small-scale instances and 20 benchmark instances. Small-scale instances can be solved directly by CPLEX through the Benders decomposition strategies to find exact solutions. The case study indicates the applicability of the G-RRVRP model and the two-stage heuristic to realistic-size problems abstracted from intercity linehaul systems. The computational experiments and case study indicate that the heuristic can solve various instances of the G-RRVRP such that the solution quality and the computation time are acceptable.

ACS Style

Hongqi Li; Xiaorong Jian; Xinyu Chang; Yingrong Lu. The generalized rollon-rolloff vehicle routing problem and savings-based algorithm. Transportation Research Part B: Methodological 2018, 113, 1 -23.

AMA Style

Hongqi Li, Xiaorong Jian, Xinyu Chang, Yingrong Lu. The generalized rollon-rolloff vehicle routing problem and savings-based algorithm. Transportation Research Part B: Methodological. 2018; 113 ():1-23.

Chicago/Turabian Style

Hongqi Li; Xiaorong Jian; Xinyu Chang; Yingrong Lu. 2018. "The generalized rollon-rolloff vehicle routing problem and savings-based algorithm." Transportation Research Part B: Methodological 113, no. : 1-23.

Journal article
Published: 01 March 2017 in European Journal of Operational Research
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ACS Style

Hongqi Li; Xinyu Chang; Wencong Zhao; Yingrong Lu. The vehicle flow formulation and savings-based algorithm for the rollon-rolloff vehicle routing problem. European Journal of Operational Research 2017, 257, 859 -869.

AMA Style

Hongqi Li, Xinyu Chang, Wencong Zhao, Yingrong Lu. The vehicle flow formulation and savings-based algorithm for the rollon-rolloff vehicle routing problem. European Journal of Operational Research. 2017; 257 (3):859-869.

Chicago/Turabian Style

Hongqi Li; Xinyu Chang; Wencong Zhao; Yingrong Lu. 2017. "The vehicle flow formulation and savings-based algorithm for the rollon-rolloff vehicle routing problem." European Journal of Operational Research 257, no. 3: 859-869.

Journal article
Published: 01 December 2016 in Transportation Research Part D: Transport and Environment
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ACS Style

Hongqi Li; Junli Yuan; Tan Lv; Xinyu Chang. The two-echelon time-constrained vehicle routing problem in linehaul-delivery systems considering carbon dioxide emissions. Transportation Research Part D: Transport and Environment 2016, 49, 231 -245.

AMA Style

Hongqi Li, Junli Yuan, Tan Lv, Xinyu Chang. The two-echelon time-constrained vehicle routing problem in linehaul-delivery systems considering carbon dioxide emissions. Transportation Research Part D: Transport and Environment. 2016; 49 ():231-245.

Chicago/Turabian Style

Hongqi Li; Junli Yuan; Tan Lv; Xinyu Chang. 2016. "The two-echelon time-constrained vehicle routing problem in linehaul-delivery systems considering carbon dioxide emissions." Transportation Research Part D: Transport and Environment 49, no. : 231-245.

Journal article
Published: 01 January 2016 in Procedia Engineering
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The combination-vehicle attributes of vehicle routing problems are additional characteristics that aim to consider more effectively the specificities of real logistics applications. Because various combination truck situations exist, the combination truck routing problem (CTRP) is supported by well-developed literature, especially with respect to the truck and trailer routing problem (TTRP), the rollon-rolloff vehicle routing problem (RRVRP), the tractor and semitrailer routing problem (TSRP), and a variety of heuristics. This article first reviews the three primary forms of the CTRP, providing a survey of problem foundations and heuristics for the TTRP, the RRVRP and the TSRP. Next, this report takes a closer look at comparing the three forms of the CTRP. The TTRP aims to efficiently apply trailers that can attach/detach trucks easily to serve less-than-truckload shipping, and the RRVRP and the TSRP aim to attain high use rates for tractors in different full truckload shipping practices. The three forms of the CTRP share a number of common features. In particular, most of the formulations and heuristic strategies developed for specific problems share many similar characteristics. The CTRP is an extremely rich and promising operations research field. More general formulations and more general-purpose solvers are necessary to address practical combination truck routing applications efficiently and in a timely manner.

ACS Style

Hongqi Li; Tan Lv; Yingrong Lu. The Combination Truck Routing Problem: A Survey. Procedia Engineering 2016, 137, 639 -648.

AMA Style

Hongqi Li, Tan Lv, Yingrong Lu. The Combination Truck Routing Problem: A Survey. Procedia Engineering. 2016; 137 ():639-648.

Chicago/Turabian Style

Hongqi Li; Tan Lv; Yingrong Lu. 2016. "The Combination Truck Routing Problem: A Survey." Procedia Engineering 137, no. : 639-648.

Research article
Published: 21 December 2013 in Discrete Dynamics in Nature and Society
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The incorporation of emissions minimization in the vehicle routing problem (VRP) is of critical importance to enterprise practice. Focusing on the tractor and semitrailer routing problem with full truckloads between any two terminals of the network, this paper proposes a mathematical programming model with the objective of minimizing emissions per ton-kilometer. A simulated annealing (SA) algorithm is given to solve practical-scale problems. To evaluate the performance of the proposed algorithm, a lower bound is developed. Computational experiments on various problems generated randomly and a realistic instance are conducted. The results show that the proposed methods are effective and the algorithm can provide reasonable solutions within an acceptable computational time.1. Introduction and Problem DescriptionAlong with the growth of the demand for goods, transportation volume is increasing rapidly. For door-to-door transportation, the most widely used mode is road transportation. However, road transportation has some negative impact on the environment because of the land use, energy resource consumption, and so forth. Road transportation accounts for almost 80% of total energy demands from transportation [1]. Fossil fuels are the main energy sources of transportation and is emitted during the combustion of fossil fuels. As a dominant mode of freight movement, road transportation accounts for the largest share of the freight-related emissions [2]. The percentages of road freight transportation emissions compared to the entire transportation sector from 1985 to 2007 in China were between 29% and 34% [3]. More and more tons of are released into the environment annually and the road freight transportation emissions are likely to keep growth. Recent studies on freight transportation have focused not only on cost minimization or profit maximization for a freight company but also on carbon reduction to enhance the corporate social responsibility for the company [4].The fuel consumption is the most expensive variable cost of the transportation process to road freight transportation enterprises [5]. The efficient use of trucks and road networks becomes more and more important. Compared with costly network infrastructure modifications, optimized routing strategies have been proven to be more efficient in enhancing network capacity [6]. Optimized vehicle routing can reduce the number of trucks and utilize the network better by reducing vehicle movements. The optimization problem has been extensively studied in the literature, known as the vehicle routing problem (VRP). The VRP and its various extensions have long been one of the most studied combinatorial optimization problems due to the problem’s complexity and extensive applications [7, 8].The incorporation of the minimization of energy and emissions in the VRP is a relatively recent topic addressed in the research work. VRP-related research that aims to minimize total fuel consumption is rather rare [9]. Kuo [9] proposed a model for calculating total fuel consumption for the time-dependent VRP. A SA algorithm was proposed. The experimental results showed that there may be a trade-off between fuel consumption, transportation time, and transportation distances. Pradenas et al. [10] presented a mathematical model for vehicle routing with time windows and backhauling. A Scatter Search (SS) metaheuristic that minimized the emission of greenhouse gases for a homogeneous vehicle fleet was designed and implemented. The experimental results showed that the environmental impacts of the vehicle routing are related to the vehicle use rate, the loads that are transported among customers, and the distances between customers.In general, various types of vehicles are used by enterprises. Through the constitution mode of the autonomous part and the nonautonomous part [11], vehicles can be classified into two main types: trucks and combination vehicles. A truck, that is, a single-unit truck, has its fixed autonomous and nonautonomous parts and the two parts cannot be separated. Within the class of combination vehicles are truck tractor-semitrailer combinations and trucks or truck tractors with semitrailers in combination with full trailers. In some extensions of the VRP, the combination vehicles, especially the use of trailers (a commonly neglected feature in the VRP), are considered. We study a variant of the combination-vehicle routing problem where tractor-semitrailer combinations are utilized. We call this variant of the VRP as the tractor and semitrailer routing problem (TSRP). As concern over global warming has grown, reducing emissions is becoming important for transportation. Minimizing fuel consumption will be increasingly influential in the VRP. Differing from other literature, we aim to minimize fuel consumption of the TSRP through considering the vehicle type and its use rate.The TSRP in the paper has the following characteristics.(1)A tractor of the tractor with semitrailer combination can pull independent semitrailers. The tractor cannot load goods and it is only used for pulling semitrailers. The time to attach/detach a semitrailer to a tractor at a location is usually considerably less than the time to load/unload all cargoes in a semitrailer, so the tractor in the TSRP has a high use rate.(2)The transportation service provider serves the customer orders from a number of depots. Shipments occur between depots and the pickup/delivery locations of an order, and between depots. Either full truckload (TL) or less than truckload (LTL) shipments may exist. Trucks considered in the VRP are fit for LTL shipments. In the TSRP, semitrailers are fit for TL.(3)The tractor and semitrailer transportation is promoted to be more energy-efficient than single-unit trucks transportation [12]. As mentioned by Ierland et al. [13], the emission factor, which can be defined as emissions per ton-kilometer (unit: g /t-km), is a typical index to describe the emission effects of the road freight transportation.(4)One of the important applications of the TSRP is the concept of multilevel freight distribution systems (e.g., city logistics and multimodal freight transportation systems), in which freight arrives at a central depot and is transported further to satellite facilities by larger vehicles, and the freight is then brought to the final customers by smaller vehicles. The problem of how to efficiently route vehicles operating at both levels is known in the literature as the Two-Echelon Vehicle Routing Problem (2E-VRP) [14], the generalized vehicle routing problem (GVRP) [15], or the single-sourcing two-echelon capacitated location-routing problem (2E-CLRP) [16]. The tractor and semitrailer combination has high average loads and a high use rate of tractors, which makes it feasible to be used in the level where shipments are large or TL.We propose the TSRP on a loaded-semitrailer flow network. There are two types of terminals on the network: one central depot and a number of satellite facilities. At the beginning, all tractors locate in the central depot, while the satellite facilities have loaded-semitrailers waiting for sending. All tractors or vehicles (a vehicle is one tractor pulling one semitrailer) originate and terminate at the central depot. A homogeneous fleet composed of tractors and semitrailers serves the flow demand among terminals. A tractor can pull one loaded-semitrailer and can also run alone. The loaded-semitrailers are assumed TL. The objective of the TSRP is to determine the number of tractors and the route of each tractor so as to minimize emissions per ton-kilometer. There are some features that distinguish the TSRP from existing research on routing problems. Firstly, we extend the application background of tractor and semitrailer combinations to the TL transportation course of multilevel freight distribution systems. The application of the TSRP is different from tractor and semitrailer combination applications in the literature, which is called the roll-on roll-off vehicle routing problem (RRVRP). Secondly, the TSRP takes a composite index, that is, emissions per ton-kilometer, as the objective. It is different from most of the VRPs which take single index (e.g., total distance, total cost, etc.) as the objective. In practice, statistical data on emissions per ton-kilometer can be used to calibrate the experimental results of the TSRP. Thirdly, the nodes of the TSRP may send more than one loaded-semitrailer and the nodes and linked arcs must be visited more than once. A node may appear more than once in the same route of the solution.Our interest in the TSRP arises from real-life regional-level truck operations in China and the TL transporting of multilevel freight distribution systems. Our aim is to develop a solving method for the TSRP and to demonstrate the effect of emission mitigation. The paper is organized as follows. The next section introduces the relevant literature. A mathematical model and a lower bound for the TSRP are developed in Section 3. Section 4 proposes the heuristic algorithm for solving the problem. Computational experiments are described in Section 5. Finally, conclusions and future work are given in Section 6.2. Literature ReviewIn this section we turn to an overview of contributions to the combination-vehicle routing problem the TSRP addresses.Research on the VRP to date has considered especially trucks, truck and full trailer combinations. The truck and trailer routing problem (TTRP) has been brought forward for decades. In the TTRP, a heterogeneous fleet composed of trucks and truck and full trailer combinations serves a set of customers. Each customer has a certain demand, and the capacities of the trucks and trailers are determinate. Some customers must be served only by a truck, while other customers can be served either by a truck or by a combination vehicle. The objective of the TTRP is to find a set of routes with minimum total distance

ACS Style

Hongqi Li; Yanran Li; Yue Lu; Qiang Song; Jun Zhang. The Effects of the Tractor and Semitrailer Routing Problem on Mitigation of Carbon Dioxide Emissions. Discrete Dynamics in Nature and Society 2013, 2013, 1 -14.

AMA Style

Hongqi Li, Yanran Li, Yue Lu, Qiang Song, Jun Zhang. The Effects of the Tractor and Semitrailer Routing Problem on Mitigation of Carbon Dioxide Emissions. Discrete Dynamics in Nature and Society. 2013; 2013 ():1-14.

Chicago/Turabian Style

Hongqi Li; Yanran Li; Yue Lu; Qiang Song; Jun Zhang. 2013. "The Effects of the Tractor and Semitrailer Routing Problem on Mitigation of Carbon Dioxide Emissions." Discrete Dynamics in Nature and Society 2013, no. : 1-14.