Branch-and-price for the pickup and delivery problem with time windows and scheduled lines

The Pickup and Delivery Problem with Time Windows and Scheduled Lines (PDPTW-SL) consists of routing and scheduling a set of vehicles, by integrating them with scheduled public transportation lines, to serve a set of freight requests within their time windows. This paper presents an exact solution approach based on a branch-and-price algorithm. A path-based set partitioning formulation is used as the master problem, and a variant of the elementary shortest path problem with resource constraints is solved as the pricing problem. In addition, the proposed algorithm can also be used to solve the PDPTW with transfers (PDPTW-T) as a special case. Results of extensive computational experiments confirm the efficiency of the algorithm: it is able to solve small- and medium-size instances to optimality within reasonable execution time. More specifically, our algorithm solves the PDPTW-SL with up to 50 requests and the PDPTW-T with up to 40 requests on the considered instances

A new approach to speed optimization of empty platform wagons in the Southeast region of Brazil / Uma nova abordagem para a otimização de velocidade de vagões de plataforma vazios na região Sudeste Do Brasil

Matching the demand for rail freight transportation depends on the railroad network structure and the availability of the rolling stock, locomotives and wagons. The distribution of wagons optimization helps reduce transportation costs, and the efficient allocation of assets is essential for rail competitiveness with other means of transportation. The present study aims to develop a mathematical model for optimizing the allocation of wagons and minimizing the distribution cost, adopted as empty transit time. The model also calculates the empty transit time of wagons according to demand distribution, and reduces the necessity for rail freight assets, because it also minimizes the wagon cycle. An algorithm was developed from the characteristics related to the distribution of freight wagons, using planned cycles adjusted by the demand distribution, and mathematical modeling was performed, applying integer linear programming to minimize the empty wagon transit time in a railway company. As a result, a weighted and optimized cycle was obtained to perform the sizing of wagons and meet the transportation plan, as well as minimizing the transit time between unloading and loading of goods. The new model presents a contribution to the operation, because, in addition to directing the optimal distribution of the assets using an integer linear programming algorithm, it also allows the planned wagon cycle adequacy, according to the demand of the respective period

Environmental and energy performance of integrated passenger–freight transport

The first-last mile (FLM) transport of passengers and freight accounts for a significant share of total transport costs, pollution, and energy consumption. According to recent scientific literature and institutional inputs at the European level, operational innovations such as the combination of passenger and freight flows may be an effective approach for promoting sustainable and energy-efficient FLM transport. In this study, the energy and environmental performances of an integrated passenger and freight transport system based on the bus network of Zrenjanin (Serbia) were investigated with different future energy mix and transport policy scenarios. The operational aspects of the integrated system were designed through collaboration with territorial stakeholders and an analysis of local planning documents. The performance was evaluated and compared with current public transport and freight schemes considering vehicle fuel and technology, total mileage, and other relevant endogenous and exogenous factors. The results of our analysis indicate operational benefits and energy savings, mainly due to reduced total mileage and the predisposition to shift to the active modes for the last mile. However, most expected long-term energy savings are the result of technological development of vehicles and modal shifts induced by policy strategies

Integration planning of freight deliveries into passenger bus networks: exact and heuristic algorithms

With the increasing population living in cities, a growing number of small daily urban freight deliveries are performed, typically by private companies. Recently, more environmentally friendly urban logistics services have emerged to mitigate the negative effects of such activities. One example is the integration of freight deliveries into bus networks, traditionally dedicated to passenger transportation, to perform urban logistics activities within cities. In this paper, the integration of the freight delivery process into the urban bus passenger network is addressed where freight parcels are dropped by clients at bus hubs located outside the city center, transported by bus services from the hub to bus stops located in the city center, and delivered to the destination address by a last mile operator. Since bus vehicles supporting both passenger and freight flows need to be physically adapted, the aim is to support the decision-maker to select the minimum number of bus services that must be adapted for freight transportation. The optimization problem considers the freight demand uncertainty in terms of number of freight parcels, destination address, delivery time windows and last mile operator constraints which are modelled by a set of demand scenarios. An exact method based on an integer linear programming (ILP) and two heuristic algorithms based on a greedy randomized adaptive search procedure (GRASP) are proposed. The results show that the proposed optimization methods are efficient, giving valuable insights to stakeholders, in the fields of policy and practice, for the strategic decision of selecting the minimum number of buses to be physically adapted for freight transportation. In particular, the results show that all proposed optimization methods are of interest in practice since the type of problem instances for which each method is more efficient is clearly identified in the obtained computational results. Moreover, in the early stages of the integrated passenger and freight flows service, the impact on the required number of adapted bus services is mainly given by the last mile operator capacity of delivering freight from bus hubs to final parcel destinations, while the other factors (delivery time windows and distributions parcel destination addresses) do not have a significant impact on the required number of bus services.publishe