Synchronizing vans and cargo bikes in a city distribution network

One of the significant side-effects of growing urbanization is the constantly increasing amount of freight transportation in cities. This is mainly performed by conventional vans and trucks and causes a variety of problems such as road congestion, noise nuisance and pollution. Yet delivering goods to residents is a necessity. Sustainable concepts of city distribution networks are one way of mitigating difficulties of freight services. In this paper we develop a two-echelon city distribution scheme with temporal and spatial synchronization between cargo bikes and vans. The resulting heuristic is based on a greedy randomized adaptive search procedure with path relinking. In our computational experiments we use artificial data as well as real-world data of the city of Vienna. Furthermore we compare three distribution policies. The results show the costs caused by temporal synchronization and can give companies decision-support in planning a sustainable city distribution concept

Analytic Hierarchy Process for City Hub Location Selection - The Viennese Case

Growing urbanization and rising urban freight volumes contribute to increasing congestion, noise and pollution which negatively impact a city’s population. City hubs are one means of mitigating this problem by consolidating goods of different suppliers at the hub and cooperating in the last mile delivery. Because of the general shortage of urban space, a major challenge is finding an appropriate location for such a hub. This paper provides a decision support tool based on the analytic hierarchy process for the hub location selection problem, which considers quantitative and qualitative criteria. By involving three stakeholder groups – the municipality, logistics companies and citizens – the approach insures a comprehensive view. The application of the model is tested for the location selection of a midi-hub – a medium-sized city hub – in Vienna. Hence, our results show that a good compromise between different stakeholder views regarding a mid-hub location selection problem can be achieved by the application of our AHP-based decision support tool

Citylogistik und intermodaler Transport als Unterstützer grüner Logistik

Logistik ist ein wichtiger Eckpfeiler der Wirtschaft, ist aber mit sehr starken negativen Auswirkungen für die Umwelt verbunden. Innovative Ideen, die die negativen ökologischen Auswirkungen der Logistik reduzieren und gleichzeitig die wirtschaftlich notwendige Gestaltung der Logistik ermöglichen, sind essenziell. In diesem Artikel werden zwei Ansätze beschrieben, wie Logistik nachhaltiger gestaltet werden kann. Auf der einen Seite wird über Citylogistik berichtet, auf der anderen Seite werden die Besonderheiten des intermodalen Verkehrs analysiert. Anschließend werden Projekte, die in letzter Zeit zu diesem Thema abgeschlossen wurden, vorgestellt. Dabei wird ein besonderer Fokus auf die Rolle quantitativer Modelle gelegt

Impact of travel time uncertainties on the solution cost of a two-echelon vehicle routing problem with synchronization

Two-echelon vehicle routing problems which contain synchronization between vehicles can be deeply impacted by time uncertainty, because one vehicle's delay can propagate to other vehicles. In this paper, we evaluate the deterministic solution of such a problem based on simulated travel time scenarios. The information obtained by simulation is incorporated in the optimization procedure iteratively. Computational results show that the degree of synchronization in an instance is directly correlated with the potential improvements by reoptimization. We present findings on the number of travel time scenarios required to obtain a representative picture of the stochastic solutions. In addition, we demonstrate that time dependent travel times can be aggregated on a city-wide level and linearized as a function of free flow times without major loss of reliability

Multi-objective optimization of a two-echelon vehicle routing problem with vehicle synchronization and "grey Zone" customers arising in urban logistics

We present a multi-objective two-echelon vehicle routing problem with vehicle synchronization and "grey zone" customers arising in the context of urban freight deliveries. Inner-city center deliveries are performed by small vehicles due to access restrictions, while deliveries outside this area are carried out by conventional vehicles for economic reasons. Goods are transferred from the first to the second echelon by synchronized meetings between vehicles of the respective echelons. We investigate the assignment of customers to vehicles, i.e., to the first or second echelon, within a so-called "grey Zone" on the border of the inner city and the area around it. While doing this, the economic objective as well as negative external effects of transport, such as emissions and disturbance (negative impact on citizens due to noise and congestion), are taken into account to include objectives of companies as well as of citizens and municipal authorities. Our metaheuristic - a large neighborhood search embedded in a heuristic rectangle/cuboid splitting - addresses this problem efficiently. We investigate the impact of the free assignment of part of the customers ("grey Zone") to echelons and of three different city layouts on the solution. Computational results show that the impact of a "grey Zone" and thus the assignment of these customers to echelons depend significantly on the layout of a city. Potentially pareto-optimal solutions for two and three objectives are illustrated to efficiently support decision makers in sustainable city logistics planning processes

Mikrodepots und Lastenräder zur innerstädtischen Güterlieferung. Eine Betrachtung am Beispiel der Stadt Wien

Die Smart City Rahmenstrategie der Stadt Wien definiert das Ziel, den Verkehr mit konventionell betriebenen Fahrzeugen zu reduzieren. Eine Möglichkeit dafür ist die Verwendung von Lastenrädern für den Gütertransport im urbanen Bereich. Doch obwohl sich das Radfahren per se in Wien immer größerer Beliebtheit erfreut, werden Lastenräder im gewerblichen Bereich noch in eher geringem Ausmaß eingesetzt. Anhand einer Literaturrecherche und ExpertInneninterviews wird aufgezeigt, wie die Situation für den kommerziellen Einsatz von Lastenrädern in Wien verglichen mit dem in Budapest, München und Kopenhagen aussieht und mit welchen Maßnahmen der gewerbliche Einsatz von Lastenrädern in Wien verstärkt werden kann. Eine zentrale Frage für den Einsatz von Lastenrädern im Speziellen zur Güterlieferung ist die der Zwischenlagerung der zu befördernden Pakete. Dieser Frage wird im zweiten Teil des Beitrags nachgegangen, wobei der Bedarf an derartigen Mikrodepots in Wien analysiert und der Bestand an adaptierbaren leerstehenden Lokalen evaluiert wird. Erste Ergebnisse zeigen einerseits Schwächen in der Radinfrastruktur in Wien, andererseits aber auch das Potential für den Lastenradeinsatz zur innerstädtischen Güterlieferung

The Two-State Prehensile Tail of the Antibacterial Toxin Colicin N

Intrinsically disordered regions within proteins are critical elements in many biomolecular interactions and signaling pathways. Antibacterial toxins of the colicin family, which could provide new antibiotic functions against resistant bacteria, contain disordered N-terminal translocation domains (T-domains) that are essential for receptor binding and the penetration of the Escherichia coli outer membrane. Here we investigate the conformational behavior of the T-domain of colicin N (ColN-T) to understand why such domains are widespread in toxins that target Gram-negative bacteria. Like some other intrinsically disordered proteins in the solution state of the protein, ColN-T shows dual recognition, initially interacting with other domains of the same colicin N molecule and later, during cell killing, binding to two different receptors, OmpF and TolA, in the target bacterium. ColN-T is invisible in the high-resolution x-ray model and yet accounts for 90 of the toxin’s 387 amino acid residues. To reveal its solution structure that underlies such a dynamic and complex system, we carried out mutagenic, biochemical, hydrodynamic and structural studies using analytical ultracentrifugation, NMR, and small-angle x-ray scattering on full-length ColN and its fragments. The structure was accurately modeled from small-angle x-ray scattering data by treating ColN as a flexible system, namely by the ensemble optimization method, which enables a distribution of conformations to be included in the final model. The results reveal, to our knowledge, for the first time the dynamic structure of a colicin T-domain. ColN-T is in dynamic equilibrium between a compact form, showing specific self-recognition and resistance to proteolysis, and an extended form, which most likely allows for effective receptor binding