Tobias Rupprecht

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.

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.

Influence of Geometry Parameters on Pedestrian Flow through Bottleneck

In pedestrian evacuations bottlenecks can be a crucial factor influencing the evacuation time. The main question involves the design of bottlenecks to enable unhindered pedestrian flow in order to optimize evacuation times. For better understanding of this problem, a set of experiments with pedestrians in different bottleneck-scenarios has been performed. The results enlarge the database and allow the testing of the basic assumptions of performance based egress design.

Empirical Study of Pedestrians' Characteristics at Bottlenecks

The design procedures of Nelson and Mowrer in the SFPE Handbook of Fire Protection Engineering (Society of Fire Protection Engineers, Bethesda, MD, 2002) and Predtetchenskii and Milinskii (PM) in Planning for Foot Traffic Flow in Buildings (Amerind, New Dehli, 1969) are frequently used for capacity analysis of pedestrian facilities, e.g. egress routes. Both agree that congestion occurs in front of a bottleneck, if the incoming flow exceeds the capacity. However, in case of a present congestion in front of a bottleneck, their approaches differ considerably. Nelson assumes that in this case the flow inside a bottleneck is determined by the bottleneck capacity. PM instead expect that the density in front of the entrance to the bottleneck is significant higher than the density, which is attributed to the capacity, and thus the flow inside is lower than the capacity. Furthermore PM assume that the density inside is generally significant lower than the density in front of the bottleneck.