Maik Boltes

New Insights into Pedestrian Flow Through Bottlenecks

Capacity estimation is an important tool for the design and dimensioning of pedestrian facilities. The literature contains different procedures and specifications that show considerable differences with respect to the estimated flow values. Moreover, new experimental data indicate a stepwise growth of capacity with width and thus challenge the validity of the specific flow concept. To resolve these differences, we experimentally studied the unidirectional pedestrian flow through bottlenecks under laboratory conditions. The time development of quantities such as individual velocities, density, and individual time gaps in bottlenecks of different widths is presented. The data show a linear growth of flow with width. The comparison of the results with experimental data from other authors indicates that the basic assumption of the capacity estimation for bottlenecks has to be revised. In contrast to most planning guidelines, our main result is that a jam occurs even if the incoming flow does not overstep the capacity defined by the maximum flow according to the fundamental diagram.

Enhanced Empirical Data for the Fundamental Diagram and the Flow Through Bottlenecks

In recent years, several approaches for modeling pedestrian dynamics have been proposed and applied e.g. for design of egress routes. However, so far not much attention has been paid to their quantitative validation. This unsatisfactory situation belongs amongst others on the uncertain and contradictory experimental data base. The fundamental diagram, i.e. the density-dependence of the flow or velocity, is probably the most important relation as it connects the basic parameter to describe the dynamic of crowds. But specifications in different handbooks as well as experimental measurements differ considerably. The same is true for the bottleneck flow. After a comprehensive review of the experimental data base we give an survey of a research project, including experiments with up to 250 persons performed under well controlled laboratory conditions. The trajectories of each person are measured in high precision to analyze the fundamental diagram and the flow through bottlenecks. The trajectories allow to study how the way of measurement influences the resulting relations. Surprisingly we found large deviation amongst the methods. These may be responsible for the deviation in the literature mentioned above. The results are of particular importance for the comparison of experimental data gained in different contexts and for the validation of models.

Automatic Extraction of Pedestrian Trajectories from Video Recordings

To understand and model pedestrian dynamics, reliable empirical data of pedestrian movement are necessary for analysis and verification, but the existing database is small, inaccurate and highly contradictory. For collecting trajectories from extensive experimental series with a large number of persons we are developing a software named PeTrack which automatically extracts these trajectories from normal video recordings with high accuracy in space and time.

Collecting pedestrian trajectories

For the proper understanding and modelling of pedestrian dynamics, reliable empirical data are necessary for analysis and verification. To this end, we have performed a series of experiments with a large number of persons. Such experiments give us the opportunity to selectively analyse parameters independent of undesired influences and adjust them to values seldom seen in field studies. We are developing software for the time-efficient automatic extraction of accurate pedestrian trajectories. Depending on the camera system the software is able to detect and track people on planar or uneven terrain with or without markers. In this paper, we summarise the experiments we have accomplished and the possibilities of our extraction techniques, in particular the newly introduced algorithm of markerless detection in stereo recordings. The markerless detection based on groups of ellipses approximating isolines of the same distance to an overhead stereo camera.

T-junction: Experiments, trajectory collection, and analysis

For the proper understanding and modelling of pedestrian dynamics, reliable empirical data is necessary for analysis and verification. This paper discusses laboratory experiments at T-junctions: the setup, the extraction of the trajectories of the pedestrians and the analysis of the resulting data. Such experiments give us the opportunity to selectively analyse parameters independent of undesired influences and adjust them to high densities seldom seen in field studies. For the T-junction the density inside the junction has been varied and analysed. Two strategies for the time-efficient automatic extraction of accurate pedestrian trajectories from stereo recordings are presented. One strategy uses marker for detection and the other one based on a perspective depth field. From these trajectories the fundamental diagram of T-junction flow is analysed, the density, velocity and specific flow profiles are obtained using the Voronoi method.

Empirical data for pedestrian flow through bottlenecks

The number of models for pedestrian dynamics has grown in the past years, but the experimental data to discriminate between these models is still to a large extent uncertain and contradictory. To enhance the data base and to resolve some discrepancies discussed in the literature over one hundred years we studied the pedestrian flow through bottlenecks by an experiment performed under laboratory conditions. The time development of quantities like individual velocities, densities, individual time gaps in bottlenecks of different width and the jam density in front of the bottleneck is presented. The comparison of the results with experimental data of other authors supports a continuous increase of the capacity with the bottleneck width. The most interesting results of this data collection is that maximal flow values measured at bottlenecks can exceed the maxima of empirical fundamental diagrams significantly. Thus either our knowledge about empirical fundamental diagrams is incomplete or the common assumptions regarding the connection between the fundamental diagram and the flow through bottlenecks need a thorough revision.

Universal flow-density relation of single-file bicycle, pedestrian and car motion

Abstract The relation between flow and density is an essential quantitative characteristic to describe the efficiency of traffic systems. We have performed experiments with single-file motion of bicycles and compared the results with previous studies for car and pedestrian motion in similar setups. In the space–time diagrams we observe three different states of motion (free flow state, jammed state and stop-and-go waves) in all these systems. Despite their obvious differences they are described by a universal fundamental diagram after proper rescaling of space and time which takes into account the size and free velocity of the three kinds of agents. This indicates that the similarities between the systems go deeper than expected.

Steps Toward the Fundamental Diagram — Empirical Results and Modelling

The empirical relation between density and velocity (fundamental diagram) of pedestrian movement is not completely analyzed, particularly with regard to the ‘microscopic’ causes which determine the relation at medium and high densities. The simplest system for the investigation of this dependency is the single-file movement. We present experimental results for this system and discuss the following observations. The data show a linear relation between the velocity and the inverse of the density, which can be regarded as the required length of one pedestrian to move. Furthermore we compare the results for the single-lane movement with literature data for the movement in a plane. This comparison shows an unexpected conformance between the fundamental diagrams, indicating that lateral interference has negligible influence on the velocity-density relation.

How Simple Hypothetical-Choice Experiments Can Be Utilized to Learn Humans' Navigational Escape Decisions in Emergencies.

How humans resolve non-trivial tradeoffs in their navigational choices between the social interactions (e.g., the presence and movements of others) and the physical factors (e.g., spatial distances, route visibility) when escaping from threats in crowded confined spaces? The answer to this question has major implications for the planning of evacuations and the safety of mass gatherings as well as the design of built environments. Due to the challenges of collecting behavioral data from naturally-occurring evacuation settings, laboratory-based virtual-evacuation experiments have been practiced in a number of studies. This class of experiments faces the traditional question of contextual bias and generalizability: How reliably can we infer humans’ behavior from decisions made in hypothetical settings? Here, we address these questions by making a novel link between two different forms of empirical observations. We conduct hypothetical emergency exit-choice experiments framed as simple pictures, and then mimic those hypothetical scenarios in more realistic fashions through staging mock evacuation trials with actual crowds. Econometric choice models are estimated based on the observations made in both experimental contexts. The models are contrasted with each other from a number of perspectives including their predictions as well as the sign, magnitude, statistical significance, person-to-person variations (reflecting individuals’ perception/preference differences) and the scale (reflecting context-dependent decision randomness) of their inferred parameters. Results reveal a surprising degree of resemblance between the models derived from the two contexts. Most strikingly, they produce fairly similar prediction probabilities whose differences average less than 10%. There is also unexpected consensus between the inferences derived from both experimental sources on many aspects of people’s behavior notably in terms of the perception of social interactions. Results show that we could have elicited peoples’ escape strategies with fair precision without observing them in action (i.e., simply by using only hypothetical-choice data as an inexpensive, practical and non-invasive experimental technique in this context). As a broader application, this offers promising evidence as to the potential applicability of the hypothetical-decision experiments to other decision contexts (at least for non-financial decisions) when field or real-world data is prohibitively unavailable. As a practical application, the behavioral insights inferred from our observations (reflected in the estimated parameters) can improve how accurately we predict the movement patterns of human crowds in emergency scenarios arisen in complex spaces. Fully-generic-in-parameters, our proposed models can even be directly introduced to a broad range of crowd simulation software to replicate navigation decision making of evacuees.

Using Stereo Recordings to Extract Pedestrian Trajectories Automatically in Space

For a proper understanding and modeling of pedestrian dynamics reliable empirical data are necessary for analysis and verification. Therefore we have performed a series of experiments with a large number of persons. For the time-efficient automatic extraction of accurate planar pedestrian trajectories we developed the program PeTrack. We now have extended the software to stereo recordings, which allows a direct height measurement without additional markers and to extract trajectories on stairs.