Exploring Perceived Vulnerability of Pedestrians: Insights from a Forced-Choice Experiment

Individual differences in mobility (e.g., due to wheelchair use) during crowd movement are not well understood. Perceived vulnerability of neighbors in a crowd could affect, for example, how much space is given to them by others. To explore how pedestrians perceive people moving in front of them, in particular, how vulnerable they believe them to be, we asked \SI{51}{} participants to complete a Two-Alternatives-Forced Choice task (2AFC) in an internet browser. Participants were shown pairs of images, each showing a person, and then asked to select the person who appeared more vulnerable to them. For example, participants would choose between a male person in a wheelchair and a female person carrying a suitcase. In total 16 different stimuli (male vs female; no item/device, 1 suitcase, 2 suitcases, small backpack, large backpack, stroller, cane, and wheelchair), yielding n(n-1)/2 = 120 potential pairwise comparisons per participant. Results showed that wheelchair users appeared the most vulnerable and persons without any items/devices the least vulnerable. Persons carrying two suitcases were in the middle. These results informed the design of a main behavioral study (not reported here)

The influence of physical and mental constraints to a stream of people through a bottleneck

Understanding movement in heterogeneous groups is important for a meaningful evaluation of evacuation prediction and for a proper design of buildings. The understanding of interactions and influencing factors in heterogeneous groups on key performance figures is fundamental for a safe design. This contribution presents results of experimental studies on movement of a crowd through a bottleneck involving participants with and without disabilities. High precise trajectories of the attendees extracted from video recordings were used to calculate density and velocity of the participants. Besides the well-established fundamental diagram new insights into the individual relation between density and velocity are discussed. A complex structure and considerate behaviour in movement implicates a strong influence of the heterogeneity on key performance values of safe movement

Together apart: the influence of increased crowd heterogeneity on crowd dynamics at bottlenecks

Individual differences in mobility (e.g., due to wheelchair use) are often ignored in the prediction of crowd movement. Consequently, engineering tools cannot fully describe the impact of vulnerable populations on egress performance. To contribute to closing this gap, we performed laboratory experiments with 25 pedestrians with varying mobility profiles. The control condition comprised only participants without any additional equipment; in the luggage condition and the wheelchair condition, two participants at the center of the group either carried suitcases or used a wheelchair. We found that individuals using wheelchairs and to a lesser degree those carrying luggage needed longer to pass through the bottleneck, which also affected those walking behind them. This led to slower times to fully clear the bottleneck in the wheelchair and luggage condition compared to the control group. The results challenge the status quo in existing approaches to calculating egress performance and other key performance metrics in crowd dynamics

The Influence of Wheelchair Users on Movement in a Bottleneck and a Corridor

Emergency exits as bottlenecks in escape routes are important for designing traffic facilities. Particularly, the capacity estimation is a crucial performance criterion for assessment of pedestrians’ safety in built environments. For this reason, several studies were performed during the last decades which focus on the quantification of movement through corridors and bottlenecks. These studies were usually conducted with populations of homogeneous characteristics to reduce influencing variables and for reasons of practicability. Studies which consider heterogeneous characteristics in performance parameters are rarely available. In response and to reduce this lack of data a series of well-controlled large-scale movement studies considering pedestrians using different types of wheelchairs was carried out. As a result it is shown that the empirical relations "mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"""mml:mover accent="false"""mml:mrow""mml:mi"ρ"/mml:mi""/mml:mrow""mml:mo"¯"/mml:mo""/mml:mover""mml:mo stretchy="false""("/mml:mo""mml:mover accent="false"""mml:mrow""mml:mi"v"/mml:mi""/mml:mrow""mml:mo"¯"/mml:mo""/mml:mover""mml:mo stretchy="false"")"/mml:mo""/mml:math" and "mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"""mml:mover accent="false"""mml:mrow""mml:msub""mml:mrow""mml:mi"J"/mml:mi""/mml:mrow""mml:mrow""mml:mi"s"/mml:mi""/mml:mrow""/mml:msub""/mml:mrow""mml:mo"¯"/mml:mo""/mml:mover""mml:mo stretchy="false""("/mml:mo""mml:mover accent="false"""mml:mrow""mml:mi"ρ"/mml:mi""/mml:mrow""mml:mo"¯"/mml:mo""/mml:mover""mml:mo stretchy="false"")"/mml:mo""/mml:math" are strongly affected by the presence of participants with visible disabilities (such as wheelchair users). We observed an adaption of the overall movement speeds to the movement speeds of participants using a wheelchair, even for low densities and free flow scenarios. Flow and movement speed are in a complex relation and do not depend on density only. In our studies, the concept of specific flow fits for the nondisabled subpopulation but it is not valid for scenario considering wheelchair users in the population. Document type: Articl

Ensuring supply for emergency services – modelling supply chains with incomplete sets of data

To ensure material availability for public health and safety services, supply chain simulation could be used to identify the risk of bottlenecks due to disruptions in global supply chains. However, these stakeholders do not have the detailed knowledge about their supply chains required for reliable simulation results. A new approach is presented in this article, which enables the modeling of a supply chain without full knowledge about each process node. It consists of generic data containers, each representing typical nodes within a supply chain with plausible process parameters, boundaries, and distributed values. We present the conceptual feasibility of the approach through a case study and demonstrate the methodology for modelling a supply chain for detailed bottleneck analysis and automated risk assessment of a public health and safety supply chain

A roadmap for the future of crowd safety research and practice: Introducing the Swiss Cheese Model of Crowd Safety and the imperative of a Vision Zero target

Crowds can be subject to intrinsic and extrinsic sources of risk, and previous records have shown that, in the absence of adequate safety measures, these sources of risk can jeopardise human lives. To mitigate these risks, we propose that implementation of multiple layers of safety measures for crowds—what we label The Swiss Cheese Model of Crowd Safety—should become the norm for crowd safety practice. Such system incorporates a multitude of safety protection layers including regulations and policymaking, planning and risk assessment, operational control, community preparedness, and incident response. The underlying premise of such model is that when one (or multiple) layer(s) of safety protection fail(s), the other layer(s) can still prevent an accident. In practice, such model requires a more effective implementation of technology, which can enable provision of real-time data, improved communication and coordination, and efficient incident response. Moreover, implementation of this model necessitates more attention to the overlooked role of public education, awareness raising, and promoting crowd safety culture at broad community levels, as one of last lines of defence against catastrophic outcomes for crowds. Widespread safety culture and awareness has the potential to empower individuals with the knowledge and skills that can prevent such outcomes or mitigate their impacts, when all other (exogenous) layers of protection (such as planning and operational control) fail. This requires safety campaigns and development of widespread educational programs. We conclude that, there is no panacea solution to the crowd safety problem, but a holistic multi-layered safety system that utilises active participation of all potential stakeholders can significantly reduce the likelihood of disastrous accidents. At a global level, we need to target a Vision Zero of Crowd Safety, i.e., set a global initiative of bringing deaths and severe injuries in crowded spaces to zero by a set year

The Influence of Individual Characteristics on Crowd Dynamics

Adequately dimensioned egress routes are important for designing safe buildings. However,their capacity analysis is usually based on studies under controlled conditions with populations defined by homogeneous movement characteristics. As a consequence, the nowadays increasing proportions of older people or persons with disabilities are not taken into account in these studies. As a result, these groups are not considered in functional relationships of pedestrian movement and therefore an issue for crowd dynamics analysis. Thus, there is a need to provide valid engineering egress data considering heterogeneous crowds, i.e. with older people and persons with disabilities. In this sense, this doctoral thesis introduces empirical insights into movement characteristics of crowds with different conditions of heterogeneity to estimate the influence of individual movement characteristics on key performance values, e.g. like speeds or flow rates. Therefore a series of studies were conducted in corridor and bottleneck situations with about 10% of participants with various disabilities and different assistive devices. These studies comprised ten to 80 participants and focused on the analysis of unimpeded speed, the individual time gap and the specific flow concept as well as the speed-density-relations and flow-density-relations. First, the unimpeded speed in the horizontal motion and its dependency on individual characteristics was determined. Second, an influence on gaps between participants and effects on the specific flow in different conditions of crowd heterogeneity was assessed. Third, empirical speed-density- and flow-density-relations were analysed to perform a capacity analysis. As a result, the diversity of individual characteristics strongly affected the local stationarity of the measures of individual velocity, density and flow rate, the dependency between density and movement speed or flow as well as increased the rate of interpersonal interactions. To integrate these results into egress calculation methods, a new analysis concept was established. Its four steps are: first, the consideration of an extended range of individual preparation times to start egress activities; second, an extended variation in distributed individual speeds; third, an adoption of empirical relations and fourth, an estimation of the flow rate based on scattered individual time gaps. Thus, this proposed concept allows the consideration of individual, heterogeneous abilities for participation in egress calculation methods

The Influence of Wheelchair Users on Movement in a Bottleneck and a Corridor

Emergency exits as bottlenecks in escape routes are important for designing traffic facilities. Particularly, the capacity estimation is a crucial performance criterion for assessment of pedestrians’ safety in built environments. For this reason, several studies were performed during the last decades which focus on the quantification of movement through corridors and bottlenecks. These studies were usually conducted with populations of homogeneous characteristics to reduce influencing variables and for reasons of practicability. Studies which consider heterogeneous characteristics in performance parameters are rarely available. In response and to reduce this lack of data a series of well-controlled large-scale movement studies considering pedestrians using different types of wheelchairs was carried out. As a result it is shown that the empirical relations and are strongly affected by the presence of participants with visible disabilities (such as wheelchair users). We observed an adaption of the overall movement speeds to the movement speeds of participants using a wheelchair, even for low densities and free flow scenarios. Flow and movement speed are in a complex relation and do not depend on density only. In our studies, the concept of specific flow fits for the nondisabled subpopulation but it is not valid for scenario considering wheelchair users in the population