Stefan Lämmer

Technische Universität Dresden | TUD · Faculty of Transportation and Traffic Science

We propose a novel self-organized traffic management strategy for incidents in traffic-light-controlled road networks. During incidents, it regulates the inflow into already congested road segments by restricting or skipping green times. Simultaneously, the remaining green times are used for the yet free turning directions. In this way, drivers can...

We propose a microscopic decision model for route choice based on discrete choice theory. The correlation of overlapping routes is included in the random portions of the utility explicitly. For computational efficiency, we restrict the choice set to the turning possibilities at the next intersection, assuming shortest paths to the destination after...

A coordination of vehicle flows is usually reached by a cyclical operation of traffic lights, and by synchronizing these cycles. The typical conditions, however, for which traffic lights are normally optimized for, never occur exactly. Large fluctuations in the number of vehicles arriving during one cycle time may lead to an inefficient usage of gr...

Human activity patterns have a multiplicity of direct links with contemporary geoscientific problems, for example, in terms of land-use due to growing urban areas, or greenhouse gas emissions due to transportation processes. Typically, the individual transportation processes are bound to a substrate (for example, a road system) which is organised a...

The growth of world population, limitation of resources, economic problems, and environmental issues force engineers to develop increasingly efficient solutions for logistic systems. Pure optimization for efficiency, however, has often led to technical solutions that are vulnerable to variations in supply and demand, and to perturbations. In contra...

The classical view of the spatio-temporal evolution of cities in developed countries is that urban spaces are the result of (centralized) urban planning. After the advent of complex systems’ theory, however, people have started to interpret city structures as a result of self-organization processes. In fact, although the dynamics of urban agglomera...

Based on fluid-dynamic and many-particle (car-following) simulations of traffic flows in (urban) networks, we study the problem of coordinating incompatible traffic flows at intersections. Inspired by the observation of self-organized oscillations of pedestrian flows at bottlenecks [D. Helbing and P. Moln\'ar, Phys. Eev. E 51 (1995) 4282--4286], we...

Self-organization is not only a feature of urban evolution, but also found within urban environments. Here, we will focus on three aspects: (i) spatiotemporal patterns in pedestrian flows and their implications for optimized pedestrian facilities, (ii) trail formation of pedestrians and their consequences for improved way systems, and (iii) a self-...

Nowadays the complexity of logistics is a buzzword spreading in business, media and everyday practice. However, the study of logistics networks from the point of view of complex dynamical systems theory has started only recently. In the past decade, physicists have been more and more interested in interdisciplinary fields such as biophysics, traffi...

A model for traffic flow in street networks or material flows in supply networks is presented, that takes into account the conservation of cars or materials and other significant features of traffic flows such as jam formation, spillovers, and load-dependent transportation times. Furthermore, conflicts or coordination problems of intersecting or me...

We study self-organization and optimization of material flows on complex networks. Two rather typical examples from the field of (socio-)economics are considered: vehicular traffic in an urban area and the production and supply of goods between cooperating manufacturers. In the case of vehicular traffic networks, traffic lights, roundabouts or oth...

IntroductionComplex Dynamics and ChaosThe Slower-is-faster Effect Observations in Traffic Systems Panicking PedestriansFreeway TrafficIntersecting Vehicle and Pedestrian StreamsRelevance to Production and Logistics Semi-conductor Chip ManufacturingContainer TerminalsPackaging and Other IndustriesAdaptive Control Traffic Equations for Production Sys...

We present a self-organising, decentralised control method for material flows in networks. The concept applies to networks where time sharing mechanisms between conflicting flows in nodes are required and where a coordination of these local switches on a system-wide level can improve the performance. We show that, under certain assumptions, the con...

The urban road networks of the 20 largest German cities have been analysed, based on a detailed database providing the geographical positions as well as the travel-times for network sizes up to 37,000 nodes and 87,000 links. As the human driver recognises travel-times rather than distances, faster roads appear to be ‘shorter’ than slower ones. The...

We present a fluid-dynamic model for the simulation of urban traffic networks with road sections of different lengths and capacities. The model allows one to efficiently simulate the transitions between free and congested traffic, taking into account congestion-responsive traffic assignment and adaptive traffic control. We observe dynamic traffic p...

We show how to treat supply networks as physical transport problems governed by balance equations and equations for the adaptation of production speeds. Although the nonlinear behavior is different, the linearized set of coupled differential equations is formally related to those of mechanical or electrical oscillator networks. Supply networks poss...

Network theory is rapidly changing our understanding of complex systems, but the relevance of topological features for the dynamic behavior of metabolic networks, food webs, production systems, information networks, or cascade failures of power grids remains to be explored. Based on a simple model of supply networks, we offer an interpretation of i...

The efficient and reliable operation of material flows in transportation networks is a subject of broad eco-nomic interest. Important applications include the control of signalized intersections in urban road systems and the planning and scheduling of logistic processes. Traditional approaches to operating material flow networks are however known t...

Die Dissertationsschrift widmet sich einer systemtheoretischen Untersuchung zur verkehrsabhängigen Steuerung von Lichtsignalanlagen in Straßennetzwerken. Aus einem mathematischen Modell für den Verkehrsablauf auf Knotenzufahrten wird ein Verfahren abgeleitet, mit dem sich Umschaltzeitpunkte und Phasenwechsel flexibel an das tatsächliche Verkehrsges...