In this paper, we present a state-of-the-art survey on the vehicle routing problem with multiple depots (MDVRP). Our review considered papers published between 1988 and 2014, in which several variants of the model are studied: time windows, split delivery, heterogeneous fleet, periodic deliveries, and pickup and delivery. The review also classifies the approaches according to the single or multiple objectives that are optimized. Some lines for further research are presented as well.

The most significant negative environmental impacts of urban trucking result largely from travel in congested traffic. To illustrate the potential of innovative solutions to this problem, this paper presents new research on the emission reductions associated with off-hour freight deliveries (OHD). The paper uses finelevel GPS data of delivery operations during regular-hours (6 AM to 7 PM), and offhours (7 PM to 6 AM), to quantify emissions in three major cities in the Americas. Using second-by-second emissions modeling, the paper compares emissions under both delivery schedules for: reactive organic gases, total organic gases, carbon monoxide, carbon dioxide, oxides of nitrogen, and particulate matter. The results show that the magnitude of the emission reductions depends on the extent of the change of delivery time. In the case of the "Full" OHD programs of New York City and São Paulo-where the deliveries were made during the late night and early morning periods (7 PM to 6 AM)-the emission reductions are in the range of 45-67%. In the case of the "Partial" OHD used in Bogotá (where OHD took place between 6 PM and 10 PM), the reductions were about 13%. The emission reductions per kilometer are used to estimate the total reductions for the cities studied, and for all metropolitan areas in the world with more than two million residents. The results indicate the considerable potential of OHD as an effectivebusiness friendly-sustainability tool to improve the environmental performance of urban deliveries. The chief implication is that public policy should foster off-hour deliveries, and all forms of Freight Demand Management, where practicable.

The location routing problem with stochastic transportation cost and vehicle travel speeds is considered in this paper. A hybrid solution procedure based on Ant Colony Optimisation (ACO) and Discrete-Event Simulation (DES) is proposed. After using a sequential heuristic algorithm to solve the location subproblem, the subsequent capacitated vehicle routing problem is solved using ACO. Finally, a DES model evaluates those vehicle routes in terms of their impact on the expected total costs. The approach is tested using well-known randomly generated datasets. Since no previous works in the literature studied exactly the same SLRP, the proposed procedure is compared against its deterministic version. Numerical results show the efficiency and efficacy of the hybrid ACO-DES approach.

La creación de centros urbanos de distribución cerca del centro de las ciudades para consolidar las cargas es una iniciativa implementada alrededor del mundo que busca mejorar la congestión del tráfico vehicular en las calles y la calidad de vida sus habitantes. Este artículo considera el problema de localización de centros urbanos de distribución y propone un modelo exacto de programación lineal entera para la toma de decisiones a nivel estratégico, táctico y operativo. Se busca resolver, de manera integral, los problemas de localización, dimensionamiento y operación (ruteo de camiones) en estas terminales logísticas. El modelo es validado usando datos de la vida real provenientes de la ciudad de Saint-Étienne, Francia. Así mismo, se realizan comparaciones experimentales con procedimientos existentes en la literatura. Los resultados muestran la eficiencia y efectividad del modelo propuesto y su aplicabilidad en la realidad para instancias hasta de tamaño mediano.