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Nonreciprocal interaction crowd systems, such as human-human, human-vehicle, and human-robot systems, often have serious impacts on pedestrian safety and social order. A more comprehensive understanding of these systems is needed to optimize system stability and efficiency. Despite the importance of these interactions, empirical research in this area remains limited. Thus, in our study we explore this underresearched area, focusing on scenarios where nonreciprocity plays a critical role, such as mass stabbings, which pose a substantial risk to public safety. We conducted the first experiments on this system and analysed high-accuracy data obtained from these experiments. The extent of the direct threat zone is determined by the speed of the moving threat and the radius of danger occurrence. We further categorize potential threats into direct, adjacent, and rear-view zones, quantifying the level of threat for pedestrians. Our study revealed that a pedestrian's desired velocity correlated positively with potential threat intensity, increasing until near the direct threat zone. An emerging steady state is observed when escape routes are blocked by moving threats. This deviation affects the density-velocity relationship, making it distinct from the general relationship. This deviation signifies unique pedestrian behaviour in the presence of moving threats. Additionally, the rate of change in the angle for pedestrian motion in various desired directions is synchronized. This indicates the emergence of collective intelligence in nonreciprocal interaction crowd systems. As a result, our study may constitute a pioneering step towards understanding nonreciprocal interactions in crowd systems through laboratory experiments. These findings may enhance pedestrian safety and inform not only government crowd management strategies but also individual self-protection measures.

Event cameras, such as dynamic vision sensors (DVS), are biologically inspired vision sensors that have advanced over conventional cameras in high dynamic range, low latency and low power consumption, showing great application potential in many fields. Event cameras are more sensitive to junction leakage current and photocurrent as they output differential signals, losing the smoothing function of the integral imaging process in the RGB camera. The logarithmic conversion further amplifies noise, especially in low-contrast conditions. Recently, researchers proposed a series of datasets and evaluation metrics but limitations remain: 1) the existing datasets are small in scale and insufficient in noise diversity, which cannot reflect the authentic working environments of event cameras; and 2) the existing denoising evaluation metrics are mostly referenced evaluation metrics, relying on APS information or manual annotation. To address the above issues, we construct a large-scale event denoising dataset (multilevel benchmark for event denoising, E-MLB) for the first time, which consists of 100 scenes, each with four noise levels, that is 12 times larger than the largest existing denoising dataset. We also propose the first nonreference event denoising metric, the event structural ratio (ESR), which measures the structural intensity of given events. ESR is inspired by the contrast metric, but is independent of the number of events and projection direction. Based on the proposed benchmark and ESR, we evaluate the most representative denoising algorithms, including classic and SOTA, and provide denoising baselines under various scenes and noise levels. The corresponding results and codes are available at https://github.com/KugaMaxx/cuke-emlb.

The existence of bottlenecks often leads to the stagnation of pedestrian gatherings, which seriously affects the efficiency of traffic and reduces the flow of pedestrians. Some studies have shown that setting devices in front of bottlenecks can promote pedestrian evacuation under certain conditions. In this paper, the effect of setting diversion devices in front of the exit on pedestrian flow is studied. From our observation, these diversion devices can form a buffer zone before the exit and affect pedestrian behaviors. The evacuation times are found to decrease as the devices became farther away from the exit. In our experiments, it is found that the effect of shunt piles on evacuation is better than in the case of safety barriers and without device conditions. Under the condition of setting up safety barriers approximately 1m and 3m in front of the exit, the evacuation times are extended by 0.88% and 2.67%. For shunt piles, the evacuation times are 11.53% and 14.96% shorter than that of those without a device regarding the different distances to exit (1m and 3m, respectively). In addition, setting up shunt piles reduces the time interval between two consecutive pedestrians. To sum up, in our experimental settings, the diversion devices can effectively improve the average speed ahead of the exit and promote evacuation to become more orderly, which reduces the congestion in the later period of evacuation. In other words, this study demonstrates that a reasonable layout of facilities can not only meet the daily functional requirements but also improve the efficient use of space in emergencies, reducing the probability of crowd conventions and jams.

Pedestrians often need to decide between different routes they can use to reach their intended destinations, both during emergencies and in their daily lives. This route-choice behavior is important in determining traffic management, evacuation efficiency and building design. Here, we use field observations and a virtual experiment to study the route choice behavior of pedestrians around obstacles delimiting exit routes and examine the influence of three factors, namely the local distance to route starting points and the pedestrian density and walking speeds along routes. Crucially, both field study and virtual experiment consider the same scenario which allows us to directly assess the validity of testing pedestrian behavior in virtual environments. We find that in both data sets the proportion of people who choose a closer exit route increases as the difference in distance between exit route starting points increases. Pedestrians' choices in our data also depend on pedestrian density along routes, with people preferring less used routes. Our results thus confirm previously established route choice mechanisms and we can predict over 74% of choices based on these factors. The qualitative agreement in results between the field study and the virtual experiment suggests that in simple route-choice scenarios, such as the one we investigate here, virtual experiments can be a valid experimental technique for studying pedestrian behavior. We therefore provide much-needed empirical support for the emerging paradigm of experiments in virtual environments.

The worldwide population is aging and countries are facing ongoing challenges in improving the safety of elderly pedestrians. In this work, single-file movement of the elderly are experimentally compared with that of different age groups. The findings indicates that the age is not the only factor influencing the pedestrian dynamics but the heterogeneity of the crowd composition and the familiarity among neighboring pedestrians also have significant effects. The existence of three regimes in the relationship between headway and speed is confirmed. In the strong constrained regime, the slope of the relationship between headway and speed of the elderly is bigger than that of the young, which means that the elders are more sensitive to the spatial headway than the young when adapting the speeds. However, the difference of the slopes in the weakly constrained regime is small, which indicates a weak dependency between age and the adaption time. The elderly need longer headway during the transformation of the motion state. Besides, the 'active cease' behavior of pedestrians, which is explained with the least effort principle, is observed in the experiment. The findings offer empirical data of the elderly under high densities and can be useful for the improvement of the pedestrian modelling and the construction of elderly friendly facilities.

The aging of population is a social phenomenon in the world. In this study, series of controlled experiments were performed to investigate the movement characteristics of elderly pedestrians passing through bottlenecks. Similar self-organized phenomena to that of the young like 'zipper effect' and 'lane formation' are observed. The highest local density that appears in front of the exit in the experiment is beyond 4 m-2. The time lapse between two consecutive pedestrians of the elderly is about 0.2 s longer than that of the young when the width is 0.5 m and 0.7 m. Besides, the difference decreases with the increasing exit width. A linear relation between flow and bottleneck width is obtained, while the flow of elders is lower than that of the young under the same width of exits. The waiting time of pedestrians can be divided into two stages when the bottleneck width is narrower than 0.8 m. The findings in this study will benefit the evacuation guidance as well as the facility design for elders., Comment: 15 pages,12 figures

Pedestrian modeling is a good way to predict pedestrian movement and thus can be used for controlling pedestrian crowds and guiding evacuations in emergencies. In this paper, we propose a pedestrian movement model based on artificial neural network. In the model, the pedestrian velocity vectors are predicted with two sub models, Semicircular Forward Space Based submodel (SFSB-submodel) and Rectangular Forward Space Based submodel (RFSB-submodel), respectively. Both unidirectional and bidirectional pedestrian flow at straight corridors are investigated by comparing the simulation and the corresponding experimental results. It is shown that the pedestrian trajectories and the fundamental diagrams from the model are all consistent with that from experiments. And the typical lane-formation phenomena are observed in bidirectional flow simulation. In addition, to quantitatively evaluate the precision of the prediction, the mean destination error (MDE) and mean trajectory error (MTE) are defined and calculated to be approximately 0.2m and 0.12m in unidirectional flow scenario. In bidirectional flow, relative distance error (RDE) is about 0.15m. The findings indicate that the proposed model is reasonable and capable of simulating the unidirectional and bidirectional pedestrian flow illustrated in this paper.

With the increase of the elderly and disabled in the world, the characteristics of pedestrian flow mixed with wheelchair users has being paid more and more attention. In this study, experiments in funnel-shaped bottlenecks were performed to study the impact of bottleneck shape and the ratio of wheelchair users on the crowd dynamics. It is found that the increase of wheelchairs in the crowd obviously leads to worse moving efficiency and congestion from the escape time, time-space relationship and time headway. Under low mixing ratios (<2.35%), less congestion occurred in the 45{\deg} bottleneck among the four tested angles (0{\deg}, 15{\deg}, 30{\deg}, 45{\deg}). The average speeds of wheelchair users is the fastest in 45 {\deg} bottleneck (0.310m/s) until the mixing ratio arrives at 7.05%. However, the advantage of the angle disappears when the mixing ratio gets higher. The findings in this study is meaningful for the guidance of pedestrian evacuation through bottlenecks with the presence of wheelchair users.

Understanding on children's movement characteristics is significant to improve their safety levels especially under emergencies. In this work, we performed laboratory experiment to investigate the dynamics of preschool children passing through bottlenecks under high movement motivation. It is found that the relations between flow and bottleneck width for adults and children can be unified when the body size and movement motivation are considered in certain way. High movement motivation leads to competition among pedestrians, which results in different spatial-temporal distribution of the density and speed compared to normal movement of adult. Based on Voronoi method, an arch-like distribution is observed for the children movement with competition, whereas it is teardrop-shaped for the adults without competition. The peak density of children, which reaches nearly 14 ped/m2, appears at the place 30 cm away from the bottleneck entrance. However, it is about 100 cm to the bottleneck for adults. Besides, several typical behaviors of children like guiding, pushing as well as playing are observed in the experiment. The findings in this study will benefit the evacuation drill design as well as the facility design for children., Comment: 17 pages, 10 figures

The worldwide population is aging and countries are facing ongoing challenges in meeting the transportation demand of the elderly. In this study, we investigate the movement characteristics of elders in the straight corridor and compare them with that of young adults. The free speeds of the elderly (about 1.28m/s) are obviously slower than that of the young people (about 1.4m/s) in the laboratory experiments. It was found that the fundamental diagram of the elderly shows the similar trend compared with that of young pedestrians. However, at the same densities the speeds of the elderly are always lower than that of the young pedestrians in the observed density range (< 3.0 m2). When the mean velocity calculated from pedestrian movement at low densities is considered, the two normalized fundamental diagrams agree quite well. The reasons for the differences are explored by analyzing the border distance, the nearest neighbors as well as the spatial distribution areas of the pedestrians. Our findings can be useful for the improvement of the pedestrian modelling and the design of pedestrian facilities that are much friendlier to the elderly., Comment: 17 pages, 15 figures