A Modification of the Social Force Model by Foresight

The motion of pedestrian crowds (e.g. for simulation of an evacuation situation) can be modeled as a multi-body system of self driven particles with repulsive interaction. We use a few simple situations to determine the simplest allowed functional form of the force function. More complexity may be necessary to model more complex situations. There are many unknown parameters to such models, which have to be adjusted correctly. The parameters can be related to quantities that can be measured independently, like step length and frequency. The microscopic behavior is, however, only poorly reproduced in many situations, a person approaching a standing or slow obstacle will e.g. show oscillations in position, and the trajectories of two persons meeting in a corridor in opposite direction will be far from realistic and somewhat erratic. This is inpart due to the assumption of instantaneous reaction on the momentary situation. Obviously, persons react with a small time lag, while on the other hand they will anticipate changing situations for at least a short time. Thus basing the repulsive interaction on a (linear) extrapolation over a short time (e.g. 1 s) eliminates the oscillations at slowing down and smoothes the patterns of giving way to others to a more realistic behavior. A second problem is the additive combination of binary interactions. It is shown that combining only a few relevant interactions gives better model performance.Comment: 6 pages, 5 figures, Preprint from PED 2008 (Wuppertal

Pedestrian flows in bounded domains with obstacles

In this paper we systematically apply the mathematical structures by time-evolving measures developed in a previous work to the macroscopic modeling of pedestrian flows. We propose a discrete-time Eulerian model, in which the space occupancy by pedestrians is described via a sequence of Radon positive measures generated by a push-forward recursive relation. We assume that two fundamental aspects of pedestrian behavior rule the dynamics of the system: On the one hand, the will to reach specific targets, which determines the main direction of motion of the walkers; on the other hand, the tendency to avoid crowding, which introduces interactions among the individuals. The resulting model is able to reproduce several experimental evidences of pedestrian flows pointed out in the specialized literature, being at the same time much easier to handle, from both the analytical and the numerical point of view, than other models relying on nonlinear hyperbolic conservation laws. This makes it suitable to address two-dimensional applications of practical interest, chiefly the motion of pedestrians in complex domains scattered with obstacles.Comment: 25 pages, 9 figure

Time-evolving measures and macroscopic modeling of pedestrian flow

This paper deals with the early results of a new model of pedestrian flow, conceived within a measure-theoretical framework. The modeling approach consists in a discrete-time Eulerian macroscopic representation of the system via a family of measures which, pushed forward by some motion mappings, provide an estimate of the space occupancy by pedestrians at successive time steps. From the modeling point of view, this setting is particularly suitable to treat nonlocal interactions among pedestrians, obstacles, and wall boundary conditions. In addition, analysis and numerical approximation of the resulting mathematical structures, which is the main target of this work, follow more easily and straightforwardly than in case of standard hyperbolic conservation laws, also used in the specialized literature by some Authors to address analogous problems.Comment: 27 pages, 6 figures -- Accepted for publication in Arch. Ration. Mech. Anal., 201

Quantitative analysis of pedestrian counterflow in a cellular automaton model

Pedestrian dynamics exhibits various collective phenomena. Here we study bidirectional pedestrian flow in a floor field cellular automaton model. Under certain conditions, lane formation is observed. Although it has often been studied qualitatively, e.g., as a test for the realism of a model, there are almost no quantitative results, neither empirically nor theoretically. As basis for a quantitative analysis we introduce an order parameter which is adopted from the analysis of colloidal suspensions. This allows to determine a phase diagram for the system where four different states (free flow, disorder, lanes, gridlock) can be distinguished. Although the number of lanes formed is fluctuating, lanes are characterized by a typical density. It is found that the basic floor field model overestimates the tendency towards a gridlock compared to experimental bounds. Therefore an anticipation mechanism is introduced which reduces the jamming probability.Comment: 11 pages, 12 figures, accepted for publication in Phys. Rev.

Statistical mechanics of non-hamiltonian systems: Traffic flow

Statistical mechanics of a small system of cars on a single-lane road is developed. The system is not characterized by a Hamiltonian but by a conditional probability of a velocity of a car for the given velocity and distance of the car ahead. Distribution of car velocities for various densities of a group of cars are derived as well as probabilities of density fluctuations of the group for different velocities. For high braking abilities of cars free-flow and congested phases are found. Platoons of cars are formed for system of cars with inefficient brakes. A first order phase transition between free-flow and congested phase is suggested.Comment: 12 pages, 6 figures, presented at TGF, Paris, 200

Resident tourists and the local 'other'

Recent years have witnessed growing numbers of residents exploring their own cities as tourist destinations. This phenomenon challenges academic understandings and definitions of who is defined as a tourist, and what differentiates tourists from residents when both display the same behaviours linked with spectacle and consumption. Of particular interest in these developments are situations where the emergence of ‘resident tourists’ involves residents transgressing boundaries of territorial stigma and fear to visit previously-avoided urban areas. Safety and security concerns and continued territorial stigma towards the Johannesburg inner city has isolated a generation of suburbanites from this urban space. Recent years have witnessed the emergence of various – often online – social media-driven (particularly Instagram) initiatives to bring these suburbanites into the inner city as resident tourists. Drawing survey data from 200 such visitors to Johannesburg’s inner city, this paper reflects on the implications for defining (proximate) tourism in terms of social or psychological rather than spatial (Euclidian) distance/proximity. In so doing, we reflect upon the role of new touristic gaze practices, inspired not only by curiosity but by a concern with self-promotion and social media self-branding. Our argument is that by rethinking emergent practices of collective consumption (facilitated in this instance by social media), we can understand how new forms of tourism occur within the locale of residence. These challenge trends towards the enclaving of daily life and mediated tourist consumption

The valuation of European financial firms

We extend the recent literature concerning accounting based valuation models to investigate financial firms from six European countries with substantial financial sectors: France, Germany, Italy, Netherlands, Switzerland and the UK. Not only are these crucial industries worthy of study in their own right, but unusual accounting practices, and inter-country differences in those accounting practices, provide valuable insights into the accounting-value relationship. Our sample consists of 7,714 financial firm/years observations from 1,140 companies drawn from 1989-2000. Sub-samples include 1,309 firm/years for banks, 650 for insurance companies, 1,705 for real estate firms, and 3,239 for investment companies. In most countries we find that the valuation models work as well or better in explaining cross-sectional variations in the market-to-book ratio for financial firms as they do for industrial and commercial firms in the same countries, although Switzerland is an exception to this generalization. As expected, the results are sensitive to industrial differences, accounting regulation and accounting practices. In particular, marking assets to market value reduces the relevance of earnings figures and increases that of equity

Statistical Models for Pedestrian Behaviour in Front of Bottlenecks

Understanding the movement of human crowds is important for our general understanding of collective behaviour and for applications in building design and event planning. Here, we focus on the flow of a crowd through a narrow bottleneck. We develop statistical models that describe how pedestrian behaviour immediately in front of a bottleneck affects the time lapse between consecutive pedestrians passing through the bottleneck. With this approach, we isolate the most important aspects of pedestrian behaviour from a number of candidate models. We fit our models to experimental data and find that pedestrian interactions immediately in front of the bottleneck appear to be less important for the observed time lapses than interactions further away from the bottleneck. Furthermore, we demonstrate how our approach can be used to rigorously compare microscopic pedestrian behaviours across different contexts by fitting the same statistical models to three separate datasets. We suggest that our approach is a promising tool to establish similarities and differences between simulated and real pedestrian behaviour

Projecting the COPD population and costs in England and Scotland: 2011 to 2030

We aimed to estimate the prevalence, healthcare costs and number of deaths among people with chronic obstructive pulmonary disease (COPD) in England and Scotland 2011-2030. We adapted the Dutch COPD Model by using English and Scottish demographic, COPD incidence, COPD prevalence, smoking prevalence and mortality data to make projections. In England, the prevalence of COPD was estimated to be 1.79% (95% uncertainty interval 1.77-1.81) in 2011, increasing to 2.19% (1.85-2.33) by 2030. In Scotland, prevalence was 2.03% (1.96-2.10) in 2011 increasing to 2.20% (1.98-2.40) in 2030. These increases were driven by more women developing COPD. Annual direct healthcare costs of COPD in England were estimated to increase from 1.50 pound billon (1.18-2.50) in 2011 to 2.32 pound (1.85-3.08) billion in 2030. In Scotland, costs increased from 159 pound million (128-268) in 2011 to 207 pound (165-274) million in 2030. The deaths in England were estimated to increase from 99,200 (92,500-128,500) in 2011, to 129,400 (126,400-133,400) by 2030. In Scotland, in 2011 there were 9,700 (9,000-12,300) deaths and 13,900 (13,400-14,500) deaths in 2030. The number of people with COPD will increase substantially over the coming years in England and Scotland, particularly in females. Services need to adapt to this increasing demand

Information use by humans during dynamic route choice in virtual crowd evacuations

We conducted a computer-based experiment with over 450 human participants and used a Bayesian model selection approach to explore dynamic exit route choice mechanisms of individuals in simulated crowd evacuations. In contrast to previous work, we explicitly explore the use of time-dependent and time-independent information in decision-making. Our findings suggest that participants tended to base their exit choices on time-dependent information, such as differences in queue lengths and queue speeds at exits rather than on time-independent information, such as differences in exit widths or exit route length. We found weak support for similar decision-making mechanisms under a stress-inducing experimental treatment. However, under this treatment participants were less able or willing to adjust their original exit choice in the course of the evacuation. Our experiment is not a direct test of behaviour in real evacuations, but it does highlight the role different types of information and stress play in real human decision-making in a virtual environment. Our findings may be useful in identifying topics for future study on real human crowd movements or for developing more realistic agent-based simulations