Universität Stuttgart
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Item Open Access Impacts of highly automated vehicles on travel demand : macroscopic modeling methods and some results(2021) Sonnleitner, Jörg; Friedrich, Markus; Richter, EmelyAutomated vehicles (AV) will change transport supply and influence travel demand. To evaluate those changes, existing travel demand models need to be extended. This paper presents ways of integrating characteristics of AV into traditional macroscopic travel demand models based on the four-step algorithm. It discusses two model extensions. The first extension allows incorporating impacts of AV on traffic flow performance by assigning specific passenger car unit factors that depend on roadway type and the capabilities of the vehicles. The second extension enables travel demand models to calculate demand changes caused by a different perception of travel time as the active driving time is reduced. The presented methods are applied to a use case of a regional macroscopic travel demand model. The basic assumption is that AV are considered highly but not fully automated and still require a driver for parts of the trip. Model results indicate that first-generation AV, probably being rather cautious, may decrease traffic performance. Further developed AV will improve performance on some parts of the network. Together with a reduction in active driving time, cars will become even more attractive, resulting in a modal shift towards car. Both circumstances lead to an increase in time spent and distance traveled.Item Open Access Potential analysis of E-scooters for commuting paths(2021) Edel, Fabian; Wassmer, Simon; Kern, MiraThe mobility needs of society are constantly increasing, resulting in congested urban areas. New mobility concepts such as e-scooters can help to reduce traffic. In particular, commuting paths, which generally remain within a specific distance, are short and manageable via an intermodal travel chain. In combination with public transport, commuting paths could be beneficial. To evaluate the potential of e-scooters used with commuting paths, a literature research focusing on mobility behavior and characteristics was conducted. In addition, an end-user survey was used to identify the ecological and economical potential for typical work routes. The research results indicate that both the mobility preferences of the users, e.g., acceptance of intermodal travel, and the technical specification of e-scooters, e.g., speed and range, meet the needs of commuting. The assessment of typical work routes shows that the use of e-scooters for the first and last mile, in combination with public transport, is highly beneficial. Furthermore, e-scooters have the potential to provide individual advantages in the areas of travel time and costs. From an ecological perspective, CO2-equivalent emissions may also be reduced for some users depending on the substituted modes.Item Open Access The risk of dissolution of sustainable innovation ecosystems in times of crisis : the electric vehicle during the COVID-19 pandemic(2021) Arribas-Ibar, Manel; Nylund, Petra; Brem, AlexanderInnovation ecosystems evolve and adapt to crises, but what are the factors that stimulate ecosystem growth in spite of dire circumstances? We study the arduous path forward of the electric vehicle (EV) ecosystem and analyse in depth those factors that influence ecosystem growth in general and during the pandemic in particular. For the EV ecosystem, growth implies outcompeting the less sustainable internal combustion engine (ICE) vehicles, thus achieving a transition towards sustainable transportation. New mobility patterns provide a strategic opportunity for such a shift to green mobility and for EV ecosystem growth. For innovation ecosystems in general, we suggest that a crisis can serve as an opportunity for new innovations to break through by disrupting prior behavioural patterns. For the EV ecosystem in particular, it remains to be seen if the ecosystem will be able to capitalize on the opportunity provided by the unfortunate disruption generated by the pandemic.Item Open Access A lower bound for the query phase of contraction hierarchies and hub labels and a provably optimal instance-based schema(2021) Rupp, Tobias; Funke, StefanWe prove a Ω(√n) lower bound on the query time for contraction hierarchies (CH) as well as hub labels, two popular speed-up techniques for shortest path routing. Our construction is based on a graph family not too far from subgraphs that occur in real-world road networks, in particular, it is planar and has a bounded degree. Additionally, we borrow ideas from our lower bound proof to come up with instance-based lower bounds for concrete road network instances of moderate size, reaching up to 96% of an upper bound given by a constructed CH. For a variant of our instance-based schema applied to some special graph classes, we can even show matching upper and lower bounds.Item Open Access Considerations about the quality assessment of travel time and travel distance distributions in transport modelling : a proposal for a standardized methodology(2020) Pestel, EricIn travel demand modelling, trip distance distributions or trip time distributions are used to evaluate how well a model fits with observed sample data. Therefore, the comparison of distributions is an essential part in the model validation process. Despite its importance, the common modelling guidelines from the UK, the USA or Austria provide little information about the correct structure and handling of such distributions. Likewise, common statistical methods are not practicable for the validation of transport models. This lack of rules leads to individual solutions, which complicate a model validation and the comparison of models. For example, when comparing two distributions the quality indicator strongly depends on the number of classes. Therefore, guidelines for model validation need to suggest an appropriate way to determine the number of classes. The paper suggests a method for evaluating trip distance distributions and trip time distributions within the model validation process of a travel demand model. It proposes (a) indicators for a classification which consider mode-specific trip distances and trip times (b) a generic classification method based on an equiquantile class width, quality indicators for comparing two distributions and (c) to use relative frequencies instead of absolute frequencies for the calculation of the quality indicators.Item Open Access Knowledge management for smart cities : standardization and replication as policy instruments to foster the implementation of smart city solutions(2023) Ruess, Patrick; Lindner, RenéAs cities tackle a variety of recent challenges, such as climate change or resilience against natural hazards, the concept of smart cities has increasingly moved into the spotlight to provide technological solutions as appropriate countermeasures. European policymakers chose the systematic funding of smart city initiatives to incentivize and accelerate innovation and sustainability transitions by disseminating knowledge, data, and information. As this undertaking is complex, there is a pressing need to involve and engage capable stakeholders to successfully implement and operate smart city projects. To ensure the diffusion and effectiveness of these initiatives, activities towards replication and standardization as knowledge management instruments have been applied in some of these research projects. However, there is a knowledge gap on how standardization can be combined with replication efforts. As one possible answer, the lighthouse project Smarter Together has actively integrated standardization in its replication activities, resulting in the development of the CEN Workshop Agreement 17381 for describing and assessing smart city solutions. The analysis of these activities resulted in the development of 11 assumptions, which show the role of standardization as a knowledge carrier for replication activities and as a facilitator for stakeholder engagement. These findings reinforce the chosen and future policy decisions.Item Open Access Vehicle scheduling for on-demand vehicle fleets in macroscopic travel demand models(2021) Hartleb, Johann; Friedrich, Markus; Richter, EmelyThe planning of on-demand services requires the formation of vehicle schedules consisting of service trips and empty trips. This paper presents an algorithm for building vehicle schedules that uses time-dependent demand matrices (= service trips) as input and determines time-dependent empty trip matrices and the number of required vehicles as a result. The presented approach is intended for long-term, strategic transport planning. For this purpose, it provides planners with an estimate of vehicle fleet size and distance travelled by on-demand services. The algorithm can be applied to integer and non-integer demand matrices and is therefore particularly suitable for macroscopic travel demand models. Two case studies illustrate potential applications of the algorithm and feature that on-demand services can be considered in macroscopic travel demand models.Item Open Access Autofreie Innenstädte: Ideen für veränderte Verkehrs- und Einkaufsstrukturen(1992) Wehking, Karl-Heinz; Hüning, ReinhardStaus und mühsame Parkplatzsuche verstärken die schädliche Emissionsbelastung, machen den Erlebnisraum Innenstadt unattraktiv und dämpfen sogar spürbar das Kaufinteresse. Neue Konzeptionen sind gefragt, eine Weiterentwicklung aussichtsreicher Ideen, um ein Verkehrs-Chaos abzuwenden und in den Innenstädten die Urbanität mit all ihren nützlichen wie geschätzten Eigenschaften zu bewahren.Item Open Access Analysis and prediction of electromobility and energy supply by the example of Stuttgart(2021) Wörner, Ralf; Morozova, Inna; Cao, Danting; Schneider, Daniela; Neuburger, Martin; Mayer, Daniel; Körner, Christian; Kagerbauer, Martin; Kostorz, Nadine; Blesl, Markus; Jochem, Patrick; Märtz, AlexandraThis paper seeks to identify bottlenecks in the energy grid supply regarding different market penetration of battery electric vehicles in Stuttgart, Germany. First, medium-term forecasts of electric and hybrid vehicles and the corresponding charging infrastructure are issued from 2017 to 2030, resulting in a share of 27% electric vehicles by 2030 in the Stuttgart region. Next, interactions between electric vehicles and the local energy system in Stuttgart were examined, comparing different development scenarios in the mobility sector. Further, a travel demand model was used to generate charging profiles of electric vehicles under consideration of mobility patterns. The charging demand was combined with standard household load profiles and a load flow analysis of the peak hour was carried out for a quarter comprising 349 households. The simulation shows that a higher charging capacity can lead to a lower transformer utilization, as charging and household peak load may fall temporally apart. Finally, it was examined whether the existing infrastructure is suitable to meet future demand focusing on the transformer reserve capacity. Overall, the need for action is limited; only 10% of the approximately 560 sub-grids were identified as potential weak points.Item Open Access Logistiksystem für den automatischen Materialfluß auf Werksgeländen(1991) Wehking, Karl-HeinzNach abgeschlossenen Testreihen mit Langzeiteinsatz in der Praxis beginnt nun die Weiterentwicklung bis zur Serienreife und die Markteinführung eines fahrerlosen Flurförderzeug-Systems - FTS mit der Typenbezeichnung Logstar - für den Betrieb auf werksinternen Straßen. Kennzeichnend für die erste Systemausführung ist der Transport von Lasten bis zu 9 t , dazu die Fahrgeschwindigkei t von 10 km/h (batteriegespeiste Antriebe) und die volle Integration in den bestehenden Werksverkehr.