Platform Screen Doors Research Articles

Improvement of Platform Screen Door System - Focus on inability to automatically open PSD -

Improvement of Platform Screen Door System - Focus on inability to automatically open PSD -

State-dependent multi-agent discrete event simulation for urban rail transit passenger flow

Urban rail transit passenger flow modeling is the foundation of urban rail transit planning, design, and operation. The motivation of this paper is to accurately and efficiently simulate passenger flow dynamics in urban rail transit systems. To this end, we propose a State-dependent Multi-agent Discrete Event Simulation (SdMaDES). The state-dependence (or congestion-dependence) means that the service abilities (or travel times) of bottleneck facilities (e.g. platform screen doors and transfer corridors) are not constant and they interact with the congestion dynamics. Specifically, we first establish a modular Multi-agent Discrete Event Simulation (MaDES), which includes four types of modules (passenger, train, station, and network modules) and three types of agents (passenger, train, and station agents). The logical connections and event-triggering modes between the modules are analyzed and defined, and thirty types of events are designed. The state-dependence is then captured by an Improved Social Force Model (ISFM), which adds an autonomous obstacle avoidance mechanism. The ISFM reproduces passenger movement behavior within bottleneck facilities of urban rail transit systems at the microscopic level. These state-dependent functions or general rules are explicitly formulated by fitting the results of ISFM and are subsequently applied to the proposed MaDES model, resulting in the SdMaDES. This integration aims to enhance the accuracy of the simulation. We conducted a real case from the Chengdu Metro network. Some interesting results are found. (a) The maximum number of boarding passengers in a train carriage is a complex nonlinear function that is dependent on the state (density inside the train carriage). This challenges the linear function commonly utilized in most studies. (b) Compared to the actual data, the proposed SdMaDES model shows a cumulative error of 9.85% after data smoothing, while the conventional MaDES model exhibits a much higher cumulative error of 21.9% after data smoothing. (c) As the overall traffic demand level increases, the gap between the two simulation models’ results is getting wider and wider due to the amplified nonlinear impact of congestion.

Experimental investigation on cooling load caused by unorganized ventilation in subway station: A case study

Unorganized ventilation significantly increases the energy consumption of subway stations. However, the quantitative description of cooling load caused by the unorganized ventilation in subway stations with platform screen doors (PSDs) still needs to be explored in depth. This study firstly proposed an experiment-based method to determine the airflow rate of unorganized ventilation, and then the corresponding cooling load is determined. Based upon this method, a series of field tests were conducted at a subway station in Shanghai. By analyzing the experimental data, the characteristic of unorganized ventilation at PSDs and entrance/exit passages was obtained. As for PSDs, the volume of unorganized ventilation in a cycle (the period from the upward train entering the station to the next upward train starting to approach the station) from the tunnel to the platform and from the platform to the tunnel is 2112.24 m3 and 4219.31 m3, respectively. With regard to entrance/exit passages, the volume of unorganized ventilation is 2655 m3 in a cycle. Thereafter, the above-mentioned results were used to determine cooling load. Owing to the difference in the departure density of train on weekdays and weekends, two typical summer days were selected for the purpose of cooling load analysis. The overall cumulative value of the cooling load caused by unorganized ventilation was 1416 kWh on a working day and 1718 kWh for the weekend, which accounted for 16.74 % and 19.19 % of the daily cooling load, respectively.

STPA-RL: Integrating Reinforcement Learning into STPA for Loss Scenario Exploration

Experience-based methods like reinforcement learning (RL) are often deemed less suitable for the safety field due to concerns about potential safety issues. To bridge this gap, we introduce STPA-RL, a methodology that integrates RL with System-Theoretic Process Analysis (STPA). STPA is a safety analysis technique that identifies causative factors leading to unsafe control actions and system hazards through loss scenarios. In the context of STPA-RL, we formalize the Markov Decision Process based on STPA analysis results to incorporate control algorithms into the system environment. The agent learns safe actions through reward-based learning, tracking potential hazard paths to validate system safety. Specifically, by analyzing various loss scenarios related to the Platform Screen Door, we assess the applicability of the proposed approach by evaluating hazard trajectory graphs and hazard frequencies in the system. This paper streamlines the RL process for loss scenario identification through STPA, contributing to self-guided loss scenarios and diverse system modeling. Additionally, it offers effective simulations for proactive development to enhance system safety and provide practical assistance in the safety field.

Numerical analysis and improvement strategy of particulate matter concentration in underground subway stations

Particulate matter (PM) is an important air pollutant in subway systems. Exposure to high PM concentrations poses a threat to human health and raises concerns. Piston effect can provide the outdoor fresh air to subway stations through station exits, but it also brings PM from tunnels to platforms when the train enters the station. In this paper, a transient numerical model is developed according to an actual subway station and validated by field tests. The model is used to investigate PM10 concentration at platform induced by train movement. The cumulative PM10 concentration at platform in one day is calculated according to the train schedule. Platform screen door (PSD) with adjustable vents is studied to control the PM10 level at platform and energy saving in 27 cities of five climatic zones in China are discussed. The results show that adjustable vent height should be less than 0.70 m to ensure that PM10 concentrations at platform can be maintained at an acceptable level and the requirement of fresh air can be met. Moreover, energy consumption can be reduced by more than 70 % in different cities compared with the conventional mechanical ventilation system. The optimized adjustable vent can provide an important reference for improving indoor air quality (IAQ) and saving energy consumption of ventilation systems in underground facilities.

A pilot study evaluating the preventive effects of platform-end lengthwise fencing on trespassing, person struck by train and traffic delays

Background: Trespassing at train tracks and “person under train” (PUT) incidents are serious health, societal and transportation concerns. There is a need for developing different measures to prevent these events. Here, we hypothesized that platform-end lengthwise fences (PLF) reduce trespassing, the number of PUT incidents (suicides and accidents), and train traffic delays. Method: PLFs were installed as the intervention at one station in Stockholm in 2020. The number of trespassers detected using CCTV-cameras was compared before and after at the intervention station over a total period of 29 months (using incidence rate ratio, IRR). The reduction in the number of PUT (over 20 years) and train traffic delays (over 9 years) was also investigated by IRR, and by using three control groups. Results: After installation of PLF there was a significant ∼90% reduction in trespasses (IRR = 0.10, 95%CI 0.04–0.23; one-sided exact p < 0.0001). No PUT incident occurred at the intervention station after the installation, compared to 1.11 per year before installation (IRR = 0.32, 95%CI 0–1.82; one-sided exact p = 0.1216). There was a significant reduction in delay minutes post installation compared to before the installation (Mann Whitney U = 0, upper one-sided exact p = 0.0357). The effect of the PLF was also observable in comparison to the three control groups, suggesting that the preventive effect was not due to wider societal events affecting all stations. Conclusion: PLF had a large effect on reducing the number of trespasses and the number of delay minutes due to trespasses and PUT incidents. PLF may also have an effect of reducing PUT incidents. Practical Applications: PLF is deemed to be relatively easy and cheap to install and thus scalable (as compared to full barriers, e.g., platform screen doors) and may be considered at platform-ends having an exit, provided there is enough space to install them.

Modeling the Duration of the Impact of Unplanned Disruptions on Passenger Trips Using Smartcard Data in Urban Rail Systems

Many urban rail systems operate near capacity given the rapid increase in passenger demand, and unplanned disruptions are unavoidable. From a passenger perspective, the duration of trip delays is a major concern, and passenger trip delays may be longer than the train delays. Several studies have focused on predicting train delays, but the research on the duration of the disruption impacts on passenger trips is limited given that the duration is not observed directly. This paper proposes a probabilistic method to estimate the disruption impact duration using smartcard data, explores statistical and machine learning models to predict the duration of impacts on passengers, and identifies influencing factors including incident characteristics, operating conditions, infrastructure, external factors, and demand. The results highlight that prediction accuracies are acceptable for multiple linear regression, accelerated failure time, and random forest models. Disruptions caused by power failures have longer impact durations than other causes, followed by platform screen doors. The fixed block signaling system leads to a larger disruption duration than the moving block system. The study provides, for the first time, a data-driven approach to understanding the duration of the impact of disruptions on passenger trips using smartcard data which can facilitate timely and informed decision-making under unplanned disruptions.

Numerical Study of Train-induced Pressure on Platform Screen Doors of a Subway Station

We numerically investigate the train-induced transient pressure on the platform screen doors (PSDs) of an island-type platform in a subway station according to real scenarios and full-scale simulation to enhance understanding of the design and safe operation of subway trains. Two typical cases, namely, the non-stop and chasing cases, were examined, with the train’s speed variation well simulated throughout both cases. In the non-stop case, a train passes through the station without stopping; in the chasing case, a train stops at the station while another subsequent train approaches through the tunnel, which inevitably happens during rush hours. It is observed that the train generates a compression wave when it passes the tunnel’s ventilation shaft, similar to what occurs when entering a tunnel. In the non-stop case, the PSDs experience two positive and one negative pressure extremes in the whole process. The first positive peak results from an oncoming compression wave through the tunnel, while the second positive and negative peaks arise due to the passing of the train head and tail, respectively. In the chasing case, the stopped train at the platform leads to a blockage effect that significantly increases the pressure on the PSDs via the oncoming compression wave. This lateral pressure may result in the failure of proper operation of the PSDs, particularly during rush hours, with pressure lasting for roughly 5.7 seconds. It is also found that, compared to the fully sealed PSD, both the half-height and partial porous PSDs can significantly reduce the pressure load caused by the passing of the train head, with its maximum pressure load reduced by 38.7% and 38.2%, respectively. Therefore, if the pressure load on a fully sealed PSD is too high for structural design, one may consider the use of half-height and partial porous PSDs as an alternative. Our study offers crucial insights into the train-induced transient pressure on PSDs in a subway station island-type platform. It provides guidance on optimizing the pressure/operation problem on PSDs and offers valuable information for the safe design and operation of subway trains.

Study on emergency ventilation strategies for various fire scenarios in a double-island subway station

The double-island subway station with complex structure and dense crowds brings about serious fire safety issues. Aiming to control fire-induced smoke, numerical simulations were conducted to investigate the emergency ventilation strategies. The numerical model was validated by the reduced-scale model experiments and full-scale experiments. Various ventilation modes were compared under different fire scenarios and platform screen door (PSD) types. The results demonstrated that a reasonable co-work mode of ventilation system was vitally important in preventing smoke dispersion and reducing pollutant concentration. Opening the screen doors was found to be conducive to the joint ventilation in the platform and tunnel under the type of full-height PSD, whereas whether opening the half-height PSD had little influence on ventilation effect. On this basis, the optimal ventilation modes were developed respectively for platform fire, fire inside the carriage and carriage fire, among which the best control measurement for carriage fire was related with the location of the train. Additionally, a reasonable optimization of the ventilation system could further improve the safe environment. This work could provide guidance for emergency response under sudden fire accident, and provide reference for engineer design of ventilation system in the metro stations.

Reducing falls among visually impaired individuals on railway platforms: Field research on environmental challenges and solutions

The aim of this study is to assess the extent to which visually impaired people are at risk of falling from railway station platforms and to identify opportunities for improvement. A barrier-finding fieldwork approach was used to conduct this study. A total of 412 stations’ platforms were examined to provide recommendations for enhancing platform safety.The study found that four major factors contribute to accidents in which visually impaired individuals may fall from railway station platforms. These factors include "the spatial layout of the platform", "the warning tactile pavers", "the Fall Prevention Hoods", and "the fall prevention fences and platform screen doors ".Based on the findings of the study, several measures are recommended to enhance the safety and accessibility of railway station platforms for visually impaired individuals. These measures include closing the gap between the platform and the train, installing Fall Prevention Hoods at lower heights near the feet so that they can be detected using a guide cane, and avoid the placement of directional tactile pavers close to the front end of the train cars or at the platform edge facing train car couplings, etc.

Toward real-time congestion measurement of passenger flow on platform screen doors based on surveillance videos analysis

Most metro stations lack automatic methods for monitoring the congestion and order of alighting and boarding passengers at each door on the platforms. Existing methods attempt to analyze historical data and predict the potential congestion but perform poorly on the burst of passengers. Furthermore, the number of passengers is the most direct indicator, but it is rough and ignores the interaction between passengers. To precisely measure the congestion of passenger flow, this paper proposes a real-time congestion measurement of passenger flow based on surveillance video analysis. First, a passengers trajectory extracting module is proposed to extract the passengers’ moving tracks from the surveillance videos. Then, the passenger flow of a train gate is treated as a bidirectional flow that goes through a bottleneck. The congestion is measured from three aspects and calculated in entropy: (1) position entropy: considering the effect of counterflow passengers (2) speed entropy: considering the effect of speed changes between passengers, and (3) angle entropy: considering the effect of the direction of passenger movement. Moreover, to improve the sensitivity of the entropy to the crowding behavior of bidirectional flows, the K-Means clustering method is applied to the speed entropy calculation process. Finally, an entropy for measuring the congestion and order of alighting and boarding passengers can be obtained. The proposed entropy measurement method is applied to the real-world data of a Guangzhou Metro station and effectively reflects the actual congestion situation.

Reducing PM10 and PM2.5 Concentrations in a Subway Station by Changing the Diffuser Arrangement.

According to the stringent regulations on particulate matter (PM) concentrations in Seoul, Korea, the PM10 and PM2.5 concentrations in subway stations must be maintained below 50 and 30 μg/m3, respectively, by 2024. Therefore, the PM concentrations in a subway station were analyzed considering air-conditioning diffuser arrangement and filtration efficiency, with the total ventilation flow rate of the station maintained constant. Dynamic analysis was performed under a worst-case scenario, wherein outdoor air was introduced through ground entrances and high-concentration dust (PM10, PM2.5) was introduced from stationary train cabins into the platforms through open platform screen doors (PSDs). Although the average PM concentrations were predicted to satisfy the reinforced criteria of Seoul under the existing operating conditions, the recommended limits were exceeded in certain local areas. To address this, the PM concentrations were predicted by changing the diffuser arrangement in the waiting room and maintaining the total ventilation flow rate constant. When the diffusers were placed near the waiting room walls, the PM10 and PM2.5 concentrations were reduced by approximately 10.5 and 5%, respectively, compared to the previous diffuser arrangement. Thus, the required PM concentration criteria were satisfied in nearly all areas of the target station, except for certain areas close to PSDs. The study findings can form the basis for improving the air quality of other subway stations.

A pilot study evaluating the effectiveness of preventing railway suicides by mid-track fencing, which restrict easy access to high-speed train tracks

Background: Suicides in the railway system is a serious health, societal, and transportation concern. Restriction of the access to suicide methods in the form of different physical barriers is a promising approach for suicide prevention. Method: Mid-track fencing, which is fencing placed in-between the high-speed and commuter train tracks, was installed at one out of seven stations along a train line outside of Stockholm in the years 2013/2014. The number of suicides at the intervention station was compared to six other stations used as controls, over a total period of 20 years (2002–2021). Results: Suicides at high-speed tracks occurring at stations was the major cause of death on the investigated railway line. Prior to the year 2014, the intervention and control stations displayed similar time trends in the number of suicides. After installation of the mid-track fencing in 2014, there was a 62.5% reduction in the rate of suicides occurring at the intervention station. Compared to the six other control stations, the intervention station displayed a significant reduction in the number of suicides during the years 2014–2021 (OR = 0.14, 95%CI 0.013–0.95). Suicides at the railway lines in-between stations were not increased post-intervention. However, nearby control stations showed a 162% increase in suicides after the intervention, suggesting the induction of transfer effects. Conclusion: Mid-track fences restricting access to high-speed train tracks may have a large effect on reducing the number of railway suicides at intervention stations, but may also induce an increase in suicides at nearby stations without mid-track fences. Practical applications: Partial physical barriers such as mid-track fencing is deemed to be relatively easy and cheap to install (as compared to full barriers; e.g., full height platform screen doors) and should be considered at all stations on railway lines that have high-speed trains passing by.

Numerical Study on the Impact of Platform Screen Doors in a Subway Station with a Train on Fire

Almost all recently built subway stations are equipped with Platform Screen Doors (PSDs) due to the numerous proven benefits of these systems. In addition, PSDs are now being introduced in existing subway stations, but their operation in conjunction with previously designed ventilation systems in case of emergency should be deeply studied. In this context, the objective of this study is to assess the efficiency of the planned emergency strategy (coupled operation, ventilation systems–PSDs system) in the case of trains on fire stopped at the platform of a subway station retrofitted with PSDs. The approach is based on Computational Fluid Dynamics (CFD) full-scale simulations to predict the airflow, temperature, and pollutant (carbon monoxide—CO and carbon dioxide—CO2) concentrations caused by the fire. The results show the evident contribution of PSDs in stopping the dispersion of hot and polluted air in the subway station during the entire simulation time (20 min from the arrival of the train on fire). Consequently, the investigated emergency strategy (exhausting air both through the “over track system” and the “under platform system”, simultaneously with the opening of the PSDs on the side with the train on fire) assures the safe evacuation of passengers as soon as they have left the subway train. The results indicate that access to the platform is not perturbed by high temperatures or dangerous concentrations of CO and CO2.

Analysis of energy-saving for ventilation and air-conditioning system of subway stations with platform screen doors

Under the background of rapid urbanization and carbon neutralization, energy-saving operation of subway stations has become a widespread concern in China. This study focused on energy-saving measures and potentials for Platform Screen Door (PSD) subway stations in various climates. To this end, theoretical-based white-box model was innovatively established and validated. Then Ventilation and Air-Conditioning (VAC) energy was extensively simulated to systematically analyze energy-saving potentials of five common measures, including mechanical fresh air supply, PSD airtightness, station temperature, Coefficient of Performance (COP) of chiller, Energy Efficiency Ratio (EER) of terminal equipment. Results show that operation measure with the greatest energy-saving potential is increasing air-conditioning temperature, with 16.9–21.0% of energy-saving potential. Besides, cancelling mechanical fresh air supply, improving COP of chiller, and improving EER of terminal equipment can bring about 11.6–20.3% of energy-savings for stations in different climate regions, whereas enhancing airtightness of PSD exerts the slightest impact on the VAC energy use, with merely 5% of energy-saving potential. Suggestions were proposed quantitatively according to effectiveness and priority of the measures, and economic benefits were discussed preliminarily. The outcomes of this study not only provide information support for governors to formulate specifications, but also provide reference for operators to take effective measures.

Energy benchmarking analysis of subway station with platform screen door system in China

The energy consumption of Ventilation and Air Conditioning (VAC) systems in subway stations has attracted much attention, aiming to figure out energy-saving potentials and improve energy efficiency. Benchmarking is a useful method to evaluate energy performance of VAC systems during the operational stage. This study describes the development of an energy benchmarking model for the analysis of VAC energy consumption in subway stations with platform screen door systems in a variety of climate regions in China. Firstly, the Constraint Value (CV) and Leading Value (LV) of VAC energy use were simulated using a validated theoretical energy model, which represent the “general” and “superior” level of the VAC energy use, respectively. Results show that, for the 2,520 simulated cases, CV ranges from 184 to 859 × 103 kWh/year and LV ranges from 178 to 529 × 103 kWh/year, with different ranges for cold, hot-summer cold-winter, and hot-summer warm-winter region. Next, the simulated values of CV and LV were applied to establish an energy benchmarking model using the ordinary least square approach. For each climate region, the regressive energy benchmarking models for CV and LV were established and validated by cross-validation. Results show that R2 are 0.753–0.903 and MBE of the test set are 2.1–7.1%, indicating a good fit for the regressive benchmarking models. In order to further test their application, the regressive models were then applied to existing subway stations. Finally, the impacts of service-related variables, i.e. number of passengers, train departure density, and tunnel length, on the CV and LV were discussed. The proposed energy benchmarking model and analysis provide a convenient and effective tool for operators and managers to evaluate VAC energy consumption status and assess energy-saving potentials for subway stations.

태풍과 고속열차 운행에 의한 지상역사 승강장 스크린도어의 풍압 수치해석 연구

In the present study, the wind pressure acting on the platform screen door is investigated numerically by a train-induced wind and a typhoon. The dual island platform on a ground-level station was considered as a computational domain. To make a stable simulation, detailed buildings and station structures were modeled in a 2 km long, 1 km wide and 200 m hight computational domain. The high-speed train and station were modeled as detail as possible, and the actual train operation was considered to build similar analysis conditions. The overset mesh method was adopted to consider the high-speed train

Characteristics of subway air quality and favorable locations for passengers waiting and taking the subway

With the increase of commuters in Beijing subway, the air quality inside subway systems has caused widespread apprehension. The particulate matter (PM) level and potential health risk of PM on the platforms and carriages of Open (O) system, Half-height platform door (HPD) system, Full-height platform door (FPD) system, Platform screen door (PSD) system were studied. The average PM2.5 concentration was approximately twice the Chinese National Ambient Air Quality Standard Class II threshold and ten times the WHO Global Air Quality Guidelines. The average PM2.5 and PM10 ratios on the platform and inside carriages were 0.81 and 0.85, respectively. Compared to the FPD and HPD, the PSD has the highest ability to prevent tunnel dust entering the platform, whereas, the FPD's preventive ability is insignificant. The maximum comprehensive indoor-air quality index (CIAI) values for platform PM2.5 and PM10 are at a very unhealthy risk level and unhealthy risk level, respectively. The average PM2.5 doses deposited by adult males in extrathoracic (ET), tracheobronchial (TB) and alveolar-interstitial (AI) during a day's round-trip ride were 163.7 μg, 9.6 μg and 24.1 μg, respectively. The PM concentration at the station platform nearer to the entrance location is greater than the middle of the platform and the center of the station hall. The PM concentration at the middle of the carriage between two doors is lower than that at the door. The research results have important guidance for constructing a subway environmental control system, station passenger flow command desk setting, passenger waiting and taking the subway to reduce the health risk.

Experimental study on transient pressure induced by high-speed train passing through an underground station with adjoining tunnels

Transient pressure variations on train and platform screen door (PSD) surfaces when a high-speed train passed through an underground station and adjoining tunnel were studied using a moving model test device based on the eight-car formation train model. The propagation characteristics of the pressure wave that was induced when the train passed through the station and tunnel at a high speed were discussed, and the effects of the train speed and station ventilation shaft position on the surface pressure distribution of the train and PSDs were analyzed and compared. The results showed that the pressure fluctuation law is different for the train and PSD surfaces, and the peak pressure increases significantly with an increase in the train speed. Ventilation shafts changed the pressure waveform on the surface of the train and PSDs and greatly reduced the peak pressure. A single shaft at the rear end of the platform and a double shaft at the station had the most significant effect on relieving transient pressure on the surface of the train and PSDs, respectively. Compared with the case with no shaft, these two shafts reduced the maximum amplitude pressure variation of the train and PSD surfaces by 46.3% and 67.4%, respectively.

YOLO-Former: Marrying YOLO and Transformer for Foreign Object Detection

The automatic detection of foreign objects between platform screen doors (PSDs) and metro train doors significantly affects personnel and property safety and maintains the train’s normal operation. However, some existing works only determine the presence of foreign objects but cannot indicate their categories. Besides, although deep-learning-based object detection algorithms can indicate the presence and categories of foreign objects, most of them only harness the information in region proposals, ignoring global contextual information. Furthermore, their performance comes at the considerable cost of computational complexity, and leading cannot be well deployed in the metro environment. To address these issues and better implement foreign object detection (FOD), we present You Only Look Once-Transformer (YOLO-Former), a simple but efficient model. YOLO-Former is accomplished based on YOLOv5 through the following procedure. First, the vision transformer (ViT) is introduced for dynamic attention and global modeling, thereby solving the problem that the original YOLOv5 only utilizes information in region proposals and has insufficient ability to capture global information. Second, the convolutional block attention module (CBAM) and Stem module are used to improve feature expression ability further and reduce floating point operations (FLOPs). Finally, we design various variants with different widths and depths to meet every need. Experiments on the foreign object detection dataset (FODD) and PASCAL VOC dataset demonstrate that YOLO-Former-x consistently outperforms other state-of-the-arts with significant margins (0.5 to 11.3 mean average precision, mAP, on FODD and 0.6 to 13.6 on PASCAL VOC dataset). Last but not least, YOLO-Former-x maintains real-time processing speed (27.32 and 28.17 frame per second, FPS, on TITAN Xp).