Platform screen doors on emergency evacuation in underground railway stations

doi:10.1016/j.tust.2011.09.003

Tunnelling and Underground Space Technology

Volume 30, July 2012, Pages 1-9

https://doi.org/10.1016/j.tust.2011.09.003 Get rights and content

Abstract

Platform screen door (PSD) systems are starting to be popular in underground railway stations. However, there is a concern that PSDs would affect passenger movement during emergency, particularly during rush hours. In this paper, the effect of PSDs on emergency evacuation under crowded conditions will be studied. The characteristics of passenger flow in crowded subway stations in Hong Kong are surveyed. Evacuation times under different passenger loadings from a train vehicle are estimated by empirical equations using the data collected from the survey. Several scenarios with different opening conditions of PSD are considered. Results are useful for working out emergency evacuation strategies for crowded subway stations.

Highlights

► Effect of platform screen doors PSDs on evacuation in underground railway stations. ► Evacuation simulation of a subway train in Hong Kong as an example. ► Evacuation time increased by 200% if door width reduced by 50% during peak hours. ► Safety management should be worked out to ensure trains stop at the right position. ► Train doors and PSDs should open simultaneously.

Introduction

Mass transit systems are operating in large cities with big underground railway systems constructed. Large numbers of passengers would move through the systems every day. Life safety in underground stations in urban cities is a concern (Qu and Chow, 2008). Fire risk in underground stations is surveyed. The environmental control system of the underground railway system is very complicated which integrates the tunnel ventilation system, smoke exhaust system, and air-conditioning system of stations. Platform screen doors (PSDs) (Wikipedia Contributors, 2009), typically with glass and stainless steel or aluminum frameworks, are used in transport systems of many large cities such as Seoul and Busan in Korea, Hong Kong and Singapore in the Far East. They are also found in Atlanta, Chicago, Denver, Newark, New York, Orlando and Seattle in the USA and Lille in France. Some of them have been used for more than 30 years.

Although many PSD systems are installed in underground railway stations all over the world, very few studies are reported on the associated operation problems. Most of the works on PSD systems were focused on two areas. The first area is the indoor environment. Energy consumption of full-height PSDs has been studied by Hu and Lee (2004) on reducing cooling load with PSD system. This topic is particularly important in dense cities with hot and humid climate such as Hong Kong and Singapore. Effective utilization of piston effects has been studied by Kim and Kim (2007) and Lin et al. (2008). PSD systems are found to be very effective in reducing energy use while operating the cooling and ventilation system of the tunnel. The second area is the safety management work to preventing railway suicides with altering human perception (Law et al., 2009). PSD system is good to avoid such incidents. However, there are deep concerns on the safety aspects of PSDs. Incidents of breaking of glass panes of PSDs were reported frequently in Hong Kong (SCMP, 2004a, Ming Pao, 2006, Oriental Daily News, 2007). Passengers on platforms with PSDs and ventilation system might take a longer time to evacuate. The time delay can be up to 350 s (Roh et al., 2009) than in the evacuation on platforms without PSDs. That was only a preliminary study without including the effect of PSDs on emergency evacuation. The problem can be very serious if the train doors and PSDs do not open at the right position as observed many times in Hong Kong and China mainland (Wen Wei Po, 2010).

In this paper, evacuation of passengers on platforms with PSDs is studied by taking the subway system in Hong Kong as an example. Passenger flow is observed to be very high during peak hours. In the morning peak hours, 8-car trains with a capacity of 2500 passengers would run at 2.1 min intervals. The loading is 70,000 passengers per hour along one direction (Hong Kong MTR Homepage, 2009). High population density would give more challenges to the emergency management of the transport system, particularly under big fires. To study the effect of PSDs on emergency evacuation, one of the most crowded stations in Hong Kong is selected. Passenger flow characteristics are surveyed first. Evacuation times under different passenger loadings from a train vehicle are then estimated from the compiled data. Several scenarios with different opening conditions of PSD are assessed.

Section snippets

Platform screen doors in emergency

PSD systems can be divided into full-height PSDs with total door height measuring from the station floor to the ceiling, and half-height PSDs which are chest-height sliding doors at the edge of the platform. Some simple platform barriers are also provided in some stations for safety. Different types of PSDs and barriers in Seoul and Busan in Korea, and in Hong Kong in China are shown in Fig. 1. All of these types of PSD systems have their benefits and drawbacks.

Full-height PSD system can

Field survey on passenger flow

In studying the crowd movement control in public transport terminals and interchanges, the maximum occupant loadings allowed in the local fire codes is considered. There are concerns that such specifications might give the worst scenario with the longest evacuation time (Chow and Ng, 2008). Design and evaluation of pedestrian facilities depends on the Level-of-Service of pedestrians as proposed by Fruin (1987) in 1971. Passenger density D is expressed as the number of passengers N (in number of

Equations for evacuation

A key factor to achieve life safety objective is to direct passengers as quickly as possible to a safe area with tenable condition under a fire. One-dimensional evacuation model by taking unidirectional evacuation paths is widely used to estimate the train evacuation time. Travel velocity is calculated as a function of density by taking movement of each passenger as motion of individuals (Nelson and Mowrer, 2003). Evacuation flow velocity V of a group is observed to be a function of the

Equations for Hong Kong

Passenger flow characteristics would be different in different places. To develop pedestrian planning standards for Hong Kong, a similar survey study was carried out on the passenger flow characteristics in the Hong Kong subway system. The velocity relationship on platform was proposed by Lam and Cheung (2000). $V (D) = \frac{1}{0.8027 + 0.9247 {(\frac{D}{2.315})}^{2.0749}}$ Another function V(D) for Hong Kong was deduced from numerical simulation with an evacuation model developed by Lo and associates later in 2004: $V (D) = \{\begin{matrix} 1.4 & D ⩽ \end{matrix}$

Train emergency evacuation

Evacuation under the situation that the train doors and PSDs do not match due to faulty operations in an emergency such as a fire is studied. Misalignment of train doors and PSDs will reduce the available doorway area as in Fig. 2c. The following assumptions are made:

•
Passengers come out of each car as soon as the train stops.
•
Passengers would not use the adjacent train vehicles for evacuation.

The width of train vehicle door available for exit l and the width of train vehicle door L for this

Station emergency evacuation

Emergency evacuation in an underground railway station should include evacuation in the platform and concourse areas. The longest travel distance will be the route from the train to the exits. For emergencies such as a fire occurred on the platform or in the train, platform evacuation would take a longer time. To study the effect of malfunctioning of PSD system on station evacuation, a typical transverse section of a station is considered. A center-platform on the platform level with an 8-car

Discussion

As observed, emergency evacuation in peak hours should not only refer to the train and station evacuation. The large amount of people on the platform should also be considered. If the train does not stop at the right position, the emergency evacuation time will be prolonged. Results show that a little reduction of exit width can lead to a longer evacuation time. Evacuation management will be made more difficult. Furthermore, passengers in crowded situations may jam at the exits. Very serious

Conclusion

PSDs are more commonly installed in underground subway stations nowadays. It provides a safer and more comfortable environment in underground railway stations, but safety concerns of such system are still limited. Evacuation of the subway train and the whole station is simulated based on the passenger flow in one of the underground railway stations in Hong Kong to study the effect of malfunctioned PSDs under crowded conditions. Results show the hazards in emergency evacuation in underground

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Platform screen doors on emergency evacuation in underground railway stations

Abstract

Highlights

Introduction

Section snippets

Platform screen doors in emergency

Field survey on passenger flow

Equations for evacuation

Equations for Hong Kong

Train emergency evacuation

Station emergency evacuation

Discussion

Conclusion

Safety Science

Energy Conversion and Management

Tunnelling and Underground Space Technology

Journal of Affective Disorders

Applied Thermal Engineering

Fire Safety Journal

Tunnelling and Underground Space Technology

Development and application of pedestrian assignment models in London railway station studies

Traffic Engineering and Control

Heat Release Rates, the SFPE Handbook of Fire Protection Engineering

Pedestrian speed/flow relationships for ground stations

Traffic Engineering and Control

Pedestrian: Planning and Design

Pedestrian speed/flow relationship for walking facilities in Hong Kong

Journal of Transportation Engineering

Review on emergency evacuation time estimation for performance-based fire safety design

Journal of Applied Fire Science