introduction · web viewan international comparison of urban rail boarding and alighting rates....

Barron, Canavan, Anderson, Cohen 1

Operational Impacts of Platform Doors in Metros

Alexander Barrona†, Shane Canavana, Richard Andersona, Judith Cohenb

aRailway and Transport Strategy Centre, Centre for Transport Studies, Dept of Civil and Environmental Engineering, Imperial College London, London, United Kingdom SW7 2AZbStrategy and Network Development, London Underground, Transport for London, London, United Kingdom SE1 8NJ

ABSTRACTPlatform doors are increasingly installed by metros, primarily to improve safety. However, they have the potential for both positive and negative operational impacts, mostly by affecting dwell times at stations. Using data from the CoMET and Nova international metro benchmarking consortia of 33 metro systems, this paper seeks to understand and quantify these operational impacts.

Overall, platform doors have a net negative impact on dwell times, leading to between 4 and 15 seconds of extra time per station stop. This is due to additional time for the larger doors to open and close slower passenger movements due to the additional distance between platforms and trains and, most importantly, extended departure delays after both sets of doors are closed caused by the need to ensure safety (that no one is trapped in the gap between the two sets of doors). This is a particular problem in mainland China, where metros conduct manual safety checks that require drivers to step out of trains onto platforms.

However, despite longer dwell times, platform doors have a net positive impact on metro operations, largely due to the many safety benefits that also reduce delays and thereby improve service performance. There are also potential benefits regarding energy and ventilation. To mitigate the negative impacts, metros should seek to refine procedures and improve technology to reduce dwell time delays caused by platform doors. Reducing or eliminating these extra delays are essential to delivering efficient service and maximum capacity, provided that safety can be assured.

SUBMISSION DATE: 23rd February 2018

WORD COUNT:

Tables: (1) 250Figures: (5) 1,250Abstract: 247Text: 5,032References: 559Total: 7,338

†Author for correspondence: Centre for Transport Studies, Imperial College London, London SW7 2AZ, UK, Tel: +44 (0)20 7594 3974, Email: [email protected].

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INTRODUCTIONPlatform doors, whether Platform Screen Doors (typically full height), Platform Edge Doors (typically half- or three-quarters-height), or Automatic Passenger Gates (typically shorter than half-height), have become commonplace elements of metro infrastructure in recent years. Although bringing marginal extra operating and maintenance costs (and a potential for failure), they are often recommended because of the wide range of benefits they bring – most notably safety (preventing suicides and trespassing on the track). Other potential benefits include improving station air-conditioning efficiency and/or supporting tunnel ventilation.

Platform doors have simultaneously both positive and negative operational impacts on dwell times at stations. They are wider than train doors so can take longer to open and close, and can lead to slower movement rates as passengers must cross two doorways to enter and leave trains. Their presence creates a risk that passengers could become trapped between the platform doors and train doors, in many cases leading to additional safety checks, which can delay trains. However, platform doors remove the risk of an incoming train striking a passenger, enabling faster platform entry speeds. In 2007, the net impact was estimated by Harris and Anderson [1]as increasing dwell times by 1-2 seconds. In the intervening years a larger and more diverse survey dataset has been accumulated; this study aims to investigate and quantify the impact of platform doors on station dwell times whilst also looking at their other overall operational impacts on metros.

The paper is structured as follows. Section 2 provides an overview of the relevant literature. Section 3 describes the data and methodology, while Section 4 presents and discusses the main results, and finally Section 5 draws together the main conclusions.

LITERATURE REVIEWThe most recognizable consequence of installing Platform Screen Doors (PSDs) is the obvious improvements they bring to safety, reducing suicides and accidents by limiting access to the track. Evidence from Hong Kong (which examined the effectiveness of installing PSDs on suicide rates) found that over an 11 year period, PSDs were responsible for a 60% reduction in railway suicides [2]. Remarkably, no significant displacement of potential attempted suicides to other platforms without platform doors was observed. However, there may be circumstances where PSDs can have a negative impact on passenger safety, for example emergency situations where passengers are evacuated. This is particularly true during peak periods. Qu and Chow [3] tested several scenarios with different passenger loading and opening conditions of PSDs. The study confirms that emergency evacuation time for trains is prolonged when PSDs are present. This is particularly sensitive to the stopping point of the train; when a train does not stop at the correct position, passenger movement can be disrupted. Reductions in exit width can lead to longer evacuation times, and in serious situations can lead to passenger panic. Additionally, evidence from Chow et al. [4], who examined incidents on fire and ventilation provision in metros in Hong Kong, further confirm the issue of aligning train to PSDs. The study also refers to reports of glass panes of PSDs breaking suddenly despite being made of toughened glass intended for extended exposure to fire, introducing an additional hazard.

PSDs do not only limit the movement of passengers; by also limiting air flow from tunnels into stations they also help control heating, ventilation and air conditioning, reducing energy use. Evidence from Taipei Mass Rapid Transit (MRT) simulations indicate that PSDs can significantly decrease the average and peak cooling load, thus reducing the capacity/size of cooling equipment and allowing the chiller cooling load to be abridged [5]. This in turn leads to

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significant savings in energy consumption. However, electricity consumption by ventilation equipment increases notably when PSDs are used.

By limiting air flow, PSDs can also shorten exposure to hazardous air pollutants. Passengers on metros can have significant exposure to Particulate Matter (PM10 and PM2.5) [6]. Evidence provided by Lee et al [7] suggests that after installing PSDs on the Seoul metro system, the average PM10 concentration on the platform without PSDs was 1.4 times higher than platforms with PSDs.

Other hazards examined include Polycyclic Aromatic Hydrocarbons (PAH) [8], as well as potential exposure to a range of metals such as iron, manganese, chromium, aluminum and copper [9-12]. Jeon et al [13] examined the levels of radon, a naturally-occurring radioactive gas which can cause lung cancer. The study of the Seoul metro system surveyed changes in radon concentrations before and after PSD installation on 54 stations across 6 lines. After implementation of PSDs the mean radon concentrations at platforms decreased by approximately 56%, from 121.7 Bq/m3 to 54.0 Bq/m3, with the number of platforms where radon concentration was 74 Bq/m3 decreasing from 38 to 12.

Additional benefits of PSDs include the effects on diffusing train noises [14]. The study found that noise levels emitted by trains was reduced by PSDs, particularly blocking the lower frequency components of train noises. In doing so this greatly improves passenger comfort.

Dwell times are by their nature random processes that depend on the number and behavior of the passengers, as well as the action of closing door and departure/take-off [15]. In terms of the impact of PSDs on boarding and alighting times, de Ana Rodríguez et al. [16] suggest that they do not have a detrimental impact on times. The findings, from both laboratory experiments as well as analysis of video footage recorded on the London Underground, indicate that the presence of the doors affects passenger behavior at the platforms, inducing a more organized boarding and alighting process. Passengers were found to wait in a more organized fashion with less clustering. Waiting beside the doors rather than in front of them allows for more room to give way to alighters more often than without PSDs. Current literature, which mostly focuses on optimizing dwell time, has examined a range of additional factors. These include, but are not limited to, Zhang et al [17], who considered individual desire, pressure from passengers behind, personal activity and tendencies (dependent on gender, age, etc.); Yalçınkaya and Mirac Bayhan [18], who considered average travel time, carriage fullness and headways; Assis and Milani [19], who considered waiting time of passengers at stations, onboard passenger comfort, train trip duration and number of trains in service; and Martinez et al [15] who considered the variability of dwell times by considering peak and off-peak hours, incidents, and other operational variables.

DATA AND METHODOLOGYWe use data from the CoMET and Nova benchmarking consortia, comprising 33 metro operators in 31 cities worldwide1. CoMET and Nova have been in existence since 1994, with the key

1 CoMET metros included in this study: Beijing BMTROC, Berlin BVG, Delhi DMRC, Guangzhou GMC, Hong Kong MTR, London Underground, Metro de Madrid, Mexico City STC, Moscow Metro, New York NYCT, Paris RATP (Metro and RER, two systems), Metro de Santiago, Metro Sao Paulo, Shanghai SSMG, Singapore SMRT and Taipei TRTC.Nova metros included in this study: Barcelona TMB, Brussels STIB, Buenos Aires Metrovias, Bangkok BEM, Istanbul Ulasim, Kuala Lumpur RapidKL, Lisbon Metro, London DLR, Montreal STM, Nanjing Metro, Newcastle Nexus, Oslo Sporveien, Metro Rio, Shenzhen SZMC, Sydney Trains, and Toronto TTC.

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objectives of comparing performance and sharing practices between metros in order to improve. The groups function within a framework of confidentiality, and a confidentiality agreement therefore governs the provided data that is referenced in this paper. This means that research results must be anonymized for publication.

This study refers to data from two principal sources: 1) a large database of survey results collected on a rolling basis over the past 15 years, and 2) questionnaire responses from a detailed case study conducted by the groups in 2013 about dwell time management. RTSC has developed a significant database of dwell time surveys carried out on a rolling basis since 2000. The full survey database includes surveys for every CoMET and Nova metro, as well as additional surveys from other metros and railways worldwide. A subset of the survey data, comprising at least one survey from each CoMET and Nova metro, was used for this analysis.

The surveys follow a standard methodology which enables direct comparisons between metros, with surveys typically carried out at the busiest station on the busiest line as the operational performance at this location determines how the overall system performs. Detailed timings are made of each element of the station stop, including wheel stop, door opening, ‘door closing’ sound, actual train door closure, and wheel start. The survey also captures passenger movements at the busiest (or most critical) door, which is the door most likely to delay the train and therefore determines the overall dwell time and, ultimately, the capacity of the line. Passenger movements recorded include the number of passengers alighting, boarding, left behind/unable to board, and those travelling in the train vestibule who may be obstructing passenger flow. Although these surveys have been carried out over many years, they accurately reflect a snapshot of on-the-ground passenger conditions and are useful for comparative purposes.

The survey data has been supplemented by questionnaires completed by many participating metros as part of a 2013 case study on Dwell Time Management. The questionnaire responses include further details of train and station operations for these busy locations with long dwell times, and also include metros’ own explanations of performance, operational experiences and perceptions. Responses from 28 metros were provided confidentially to the consortia for the case study.

RESULTS AND DISCUSSIONThe key operational impacts of platform doors on metros are with regard to dwell times (station stop times), safety, and energy. We find that platform doors have a net negative impact on station dwell times, adding 4-15 seconds on average. However, despite the longer dwell times, we find that platform doors have a net positive overall impact on metros, primarily because of the dramatic reduction in track intrusions (to near zero) and the potential to save energy. These other benefits are especially relevant where track intrusion is a problem, such as high rates of suicides or trespassers that is more common in Europe and North America, or where stations are air-conditioned, as is common for underground stations in most Asian metros. Each of the constituent impacts will be discussed in the sub-sections below.

Impacts on Dwell TimesThe most important impact of platform doors on metro operations is dwell times (the time that trains are stopped in stations). Dwell time can be defined as the total time from the wheels stopping to the wheels starting to move again. Platform doors impact dwell times in several different ways, with the net impact not entirely clear.

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Opening and closing timesBecause platform doors are larger and slower than train doors, they typically take longer to open and close. A sample of door width data for six metros with platform doors from the survey shows that platform doors ranged from 22-48% wider than the corresponding train doors, and were above 2m wide in all but one of the metros. Although this is necessary to allow for the stopping tolerance of the train, it does also mean that the doors are bigger and slower (and also easier to block).

Figure 1 below shows the observed door opening times at busy metros stations worldwide from the surveys. Although there is overlap of door opening times of between 3 and 4 seconds for both with and without PSDs, it is clear that the presence of PSD generally adds to door opening times. Opening times of 2-4 seconds are typical without platform doors, whereas times are typically 3-5 seconds with platform doors. In some cases, platform doors open and close after train doors, which causes the process to take even longer. For the metros with very short door opening times below (e.g. zero or one second), the doors may begin opening before the train wheels come to a complete stop – this can sometimes be found on older trains in older metros. Based on these observations, we estimate that the longer opening and closing times add approximately 1-2 seconds to station dwell times with platform doors.

Passenger flow ratesPassenger flow rates (for both boarding and alighting from trains) are influenced by a wide variety of factors, including the precise geometry of each station and train surveyed, passenger volumes, and cultural factors. These boarding and alighting rates have been observed at metros worldwide through the survey process. Statistical tests using regression analysis were conducted, but the results relating to platform doors were inconclusive. This was partly due to the relatively small number of observations with platform doors in the entire sample, but also because of the diversity of the sample. For example, platform doors are more prevalent in Asian metros, where passenger volumes are higher and passenger flow rates may be proportionally higher than elsewhere (with or without platform doors).

However, anecdotal observations from surveys and individual survey results suggest that passenger movements are generally slightly slower with platform doors. This is primarily because of the slightly greater distance from the platform to the train, and the related need for passengers to pass through two sets of doors and thresholds instead of just one. On average, boarding and alighting rates are both approximately 1.1 passengers per second per door. Even if these passenger flow rates are only 10% slower (i.e. 1.0 passengers per second rather than 1.1), the aggregate effect on dwell times can be significant. With a hypothetical flow of 30 passengers (combining boarders and alighters) at a busy interchange station, a 10% reduction in the movement rate would lead to an additional 2-3 seconds. It is also important to note that this situation only has to occur at one door of the train (the busiest door) to cause the dwell time increase.

Departure delayThe most significant impact of platform doors on dwell times is due to departure delay, which is the time between the final door closing and the train starting to move (after both the train and platform doors are closed). These delays have been observed to be very significant in some

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metros, as illustrated in Figure 2 below. All of the examples highlighted in the figure are using Automatic Train Operation (ATO), with the ‘best practice’ example of Shanghai Line 10 is now operating in full automatic mode (UTO)..

It is normal for there to be some small amount of post-door closing delay for all metros. This time is spent confirming that all doors are closed and locked and that it is therefore safe to depart. First, there can be some technical delay during which the door status is communicated throughout the train. On lines with drivers, there can also be delay whilst the driver observes this doors closed/locked notification and/or makes their own observations, such as using cameras or platform mirrors. In some cases, the design of the cab may contribute to longer dwell time if the operation requires the driver to move away from their seat. In more traditional circumstances, with a driver and no platform doors, we have observed this delay to be, on average, approximately 5 seconds at busy stations during peak hours, although it can range from as short as 2-3 seconds up to 10-12 seconds.

With platform doors, this procedure is complicated by having a second set of doors that need to be confirmed to be closed and locked, but also – most importantly – by having a gap between the platform doors and the train. With platform doors, we have observed the post-door closure delay to be on average 12 seconds worldwide, but with a very wide range of between 3 and 25 seconds. However, the variation observed has been clearly divided between observations in mainland China and elsewhere.

Outside of China, the observed delay has ranged from approximately 5-10 seconds, with 6 seconds suggested to be good practice. In these cases, the presence of platform doors is only adding approximately 1-2 seconds to station dwell times compared to stations without platform doors. In mainland China, however, the observed delay has ranged from 10 to 25 seconds, with 15 seconds being the most typically observed value. The reason for these significant delays is the extensive manual checking procedures in place for the gap between the platform doors and the train. Typically, the driver must physically step out of the train onto the platform and conduct a series of maneuvers to check no one is trapped in the gap between the platform doors and the train (before then re-entering the train and preparing to drive off), as shown in Figure 3 below. This procedure was introduced to ensure safety, and is practiced partly because of two known cases in China (2007 in Shanghai and 2014 in Beijing) where a passenger became trapped between closed train and platform doors and was ultimately killed.

It is important to consider the implications of this practice. Although it may help to ensure safety, the resulting delays also have significant costs, both in terms of metro capacity and passenger time. If the departure delay in Chinese metros could be reduced from the current typical value of 15s to the 6s observed good practice value from elsewhere in the world – thus saving 9s per station stop – an additional one or two trains per hour could be operated, providing valuable extra capacity for very crowded lines. Alternatively, if a typical line has 30 stations, then saving 9s per station would save 4.5 minutes from one end of the line to another, which for many lines would be enough in the peak (when frequencies may be 2-3 minutes) to enable the same service to operate with fewer resources (for example, one fewer driver and/or train).

However, the greater impact may be in the value of lost time for passengers. If we consider a hypothetical example in Shanghai, we can attempt to calculate a value for the time lost. If the average passenger travels through approximately 8 stations and experiences the same extra time loss of 9s per station as explained above, then 72s would be lost per journey. With an average of nearly 5 million passenger journeys per day, which suggests about 100,000 hours of customer time may be lost per day. If the average value of time is assumed to be equal to the

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average net city wage in Shanghai (US$5.21 in 2015 US$ PPP terms [20]), then the value of time lost per day is US$521,000, or nearly US$200m per year.

This hypothetical example is used to illustrate the cumulative effect that such seemingly small impacts have. It is important also to consider the broader impacts of these costs on cities. Any passengers discouraged from travelling by metro (either because of the lost time or, more likely, the lack of available capacity) who therefore travels by other modes is likely to reduce overall safety, because other transport modes are almost certainly less safe than metros. Those same potential passengers may also create additional costs by contributing to road congestion. It is hoped that this example illustrates how calculating the economic cost of delays can produce powerful data showing exactly how much is the value of time lost. This data can be shown to senior management and governments, and can potentially help persuade them to change policies or regulations, or to invest in technology that would reduce or even eliminate the problem.

One observed exception to these significant departure delays has been observed in China, however – on Line 10 in Shanghai. Line 10 was originally designed for future fully automated (UTO/GoA4) operations, and in August 2014 Shanghai Metro began live testing of a more automatic mode. This new operating mode includes fully automated dwell times, where the station stop is managed completely by the computer, and the system handles ensuring safe departure using a series of interlocked systems and sensors for train doors, platform doors, and gap detectors (see Figure 4). If ultimately successful, this solution has great potential to eliminate the long delays experienced in China, which would both improve capacity and save significant sums of money in passenger time. However, it is still under evaluation, and the costs to implement similar systems on other metro lines may be significant. Still, in the future as infrastructure and equipment ages and ultimately is refurbished or replaced, installing such systems may be advisable.

Other factorsAlthough issues related to the opening and closing of doors, passenger flow rates, and departure delays are the most important impacts, platform doors can also impact dwell times by impacting passenger behavior and the consistency of dwell times. Some metros – particularly those with platform doors on only small proportions of their network, or only on new lines – have reported better passenger behavior with platform doors. Although we do not have any concrete data to support or refute this, it is believed that this may be a reflection of the different equipment. For example, passengers may recognize the need to pass through (or hold) two sets of doors to be more intimidating than just one, and therefore be more timid about taking disruptive actions. Furthermore, passengers may (even subconsciously) associate new platform doors with more technology and automation and consider that it is advisable to not challenge them. (Conversely, if passengers know that a driver is manually closing the doors and looking at them from the front of the train, they may believe that the driver will wait or reopen the doors for them.)

In addition, there could be positive impacts associated with passengers being sure of where the train doors will be and lining up accordingly, which may actually improve passenger flow when trains arrive. Without platform doors, passengers will not know exactly where the train doors will be located (and train stopping positions may be more variable, particularly with manual driving), which may lead to some delay as passengers re-align themselves with the door. However, this situation may actually be less relevant for very busy stations, where passengers who could not board a previous train will already be lined up by the door positions, and can also

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be mitigated by using platform markings. Anecdotal observations from surveys suggest that this characteristic generally has a positive, but very marginal, impact on dwell times.

Finally, there is evidence to suggest that platform doors may make station dwell times more consistent, which in turn improves the overall regularity of train service. In the survey dataset, the coefficient of variation of station stop times was about 37% better with platform doors than without. However, it is important to recognize that this association is likely also linked to age of equipment, level of automation, and the fact that more platform doors are present in Asian metros, where service is overall significantly more reliable. Still, greater regularity of dwell times would be consistent with better passenger behavior, and some metros who are planning to retrofit platform doors have reported that they are expecting to achieve more consistent (if slightly longer) dwell times.

Impacts on SafetyImproving safety is typically a key reason to implement platform doors in metros, and there is no doubt that platform doors improve safety significantly. Based on a previous safety study conducted by the CoMET and Nova groups in 2011, it is clear that with platform doors there is a dramatic reduction in track intrusions to nearly zero. This reflects not only suicides and suicide attempts but also passengers hit by trains, passengers falling onto the track, and passengers trespassing on the track. The physical separation of the track right-of-way from the platform, strongest with full-height PSDs, is crucial for eliminating both intentional and unintentional intrusions. There can also be improvements in other related issues, such as track fires (as significantly less litter from passengers can actually reach the track).

The only related safety indicator that did not improve with platform doors was the number of passengers caught in doors. In fact, this indicator actually increased, which can be explained by the presence of two sets of doors for passengers to get caught in, and perhaps in some cases the big and slow nature of platform doors attracting passengers to try and hold them or pass through them as they are closing.

The other safety-related issue to mention is the potential for passengers to get trapped in the gap between the train and the platform doors. Although very dangerous, the number of instances appears to be very low. There seems to be only two reported occurrences worldwide – one in Shanghai in 2007, one in Beijing in 2014 (both of which unfortunately resulted in the death of the passenger). This risk can be mitigated by design, ensuring that the gap is as small as possible and that platform doors have taper plates that prevent closure if someone is standing in the gap, and by technology, using systems such as laser detectors (like the ones on Shanghai Line 10 shown in Figure 4) to confirm that the gap is clear before the train departs.

Apart from the safety benefits of platform doors, it is important to recognize the benefits of reduced safety-related incidents on train service. The negative impacts of delays associated with these incidents are massive – for example, entire metro lines may be shut down for hours after a suicide, and trespassers may require power to be turned off and police to search tunnels. By virtually eliminating these incidents and the related delays, the metro and all passengers benefit significantly. In fact, the costs associated with retrofitting platform doors may be able to be justified on the savings linked to fewer disruptions (when also considering the value of time lost by passengers).

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Impacts on EnergyAlthough not the focus of the surveys referenced in this paper, it has been observed that platform doors can lead to energy savings for metros. This is especially true where underground stations are air-conditioned, as platform doors retain the cool air in the station and avoid leakage into the tunnels. To achieve these savings, the stations needs to be completely sealed off from the tunnels with full-height PSDs. Evidence from Hu and Lee [5], which carried out a case study on the Taipei MRT system, estimate that in the peak periods the case without PSDs can experience as much as 50% more electricity consumption of the case with PSDs..

Even for metros without air-conditioned stations, platform doors may help achieve some savings – for example, by contributing to a metro’s overall approach to ventilation. However, this is very dependent on the metro’s existing ventilation setup, and therefore the impact of platform doors may vary significantly.

Other ImpactsFinally, this section summarizes other operational impacts of platform doors in metros:

If metros have manual driving, then platform doors can enable faster train speeds when entering stations. Anecdotal evidence from surveys suggests that this could potentially save two seconds per station. However, it is important to note that this could also be done with automatic driving (i.e. ATO) without platform doors.

Increased investment and maintenance costs are required to purchase, install, and maintain platform doors. In particular, retrofitting platform doors can be very expensive, as platforms may need structural works to support the additional weight and cantilevered loads, and there may be challenges associated with overhead obstructions or curved platforms.

Platform doors introduce another piece of equipment that can fail, which can cause delays – although long-term data from CoMET and Nova suggest that the number of delays caused by platform doors are very small.

Platform doors can help to prevent objects, including trash, from reaching the track. This in turn reduces the delays associated with retrieving or removing objects as well as the prevalence of track fires.

Space may be better utilized on platforms with platform doors, as passengers can safely use all of the space up to the edge. This may in turn increase platform capacity and reduce any need to restrict access to stations due to crowding. However, anecdotal evidence, including that from Figure 5, below suggests that perhaps the queuing encouraged by platform doors also means that platform space between doors is actually less used.

CONCLUSIONSWe have seen that platform doors have significant operational impacts for metros, most importantly relating to dwell times and safety, but also to other factors such as energy and possibly passenger behavior. Overall, we find that platform doors have a net negative impact on dwell times, adding between 4 and 15 seconds on average to the time trains are stopped at each station. This additional time adds up to significant lost time for passengers, and can also lead to reduced total capacity provided. The key factors leading to longer dwell times with platform doors and the average impact compared to stations without platform doors are summarized in Table 1 below.

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However, despite these longer dwell times, we find that platform doors have a net overall positive impact on metros, primarily due to the significant safety benefits. These include both the reduction in safety incidents themselves, in which platform doors virtually eliminate track intrusions (and therefore nearly all suicides and cases of passengers being hit by trains), but also the significant reductions in delays associated with safety incidents. It is also important to acknowledge that platform doors may lead to more consistent, regular dwell times, and help to enable higher degrees of automation, both of which improve overall service performance.

To retain the positive benefits and mitigate the negative impacts, metros should seek to refine procedures and improve technology to reduce dwell time delays caused by platform doors. The main example of this is the significant departure delay experienced primarily in mainland China, where delays of typically 15 seconds, but as high as 25 seconds, are experienced after both train and platform doors are closed and before the train begins to move. Reducing or eliminating these extra delays are essential to delivering efficient service and maximum capacity, provided that safety can be assured. For metros considering platform doors – either for new lines or retrofitting for existing lines – it is important to consider these impacts at the planning stage, noting that the significant benefits of platform doors may justify the not insignificant costs of installation.

ACKNOWLEDGEMENTSWe would like to thank the metros of the CoMET and Nova consortia for supporting this research, including by their responses to the case study questionnaire and participation in the on-site surveys.

The authors confirm contribution to the paper as follows: study conception and design: Alexander Barron, Richard Anderson; data collection: Alexander Barron, Judith Cohen; analysis and interpretation of results: Alexander Barron, Shane Canavan, Richard Anderson, Judith Cohen; draft manuscript preparation: Alexander Barron, Shane Canavan. All authors reviewed the results and approved the final version of the manuscript.

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Met

ro O

bser

vatio

nsDoor Opening Times0

0

With platform doorsNo platform doors

Figure 1 Observed Door Opening Times (based on RTSC surveys at busy metro stations worldwide, 2000-2013)

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Figure 2 Observed departure delay worldwide at busy stations during peak hours (based on RTSC surveys)

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Figure 3 Example of Chinese metro driver checking procedure (taken in Guangzhou Metro by RTSC, 2014)

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Figure 4 Interlocked gap detection system using lasers on Shanghai Metro Line 10 (photo taken by author, 2014)

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Figure 5 Passengers queuing at platform doors in London, showing how queues lead to inefficient use of platform space (photo taken by author, 2013)

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Table 1 Summary of key dwell time factors influenced by platform doors

Factor Average Impact

Slower door opening and closing times + 1-2 seconds

Slower passenger flow rates (boarding and alighting) + 2-3 seconds

Longer departure delay after all doors closed +1-10 seconds

PLATFORM DOORS +4-15 seconds

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introduction · web viewan international comparison of urban rail boarding and alighting rates....

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