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Trap & Drag
A Systemic Breakdown Analysis of the 2015 West Wickham Incident


Scope: Systems Analysis, Accident Investigation, Human Factors 

Role: Preliminary Research on Trap & Drag, Methodology selection,

System breakdown and analysis, Recommendations

Duration: 96 hours

Team: Individual work


In the aftermath of an incident, it is often tempting to attribute blame to individuals or dismiss it as a mere accident, overlooking the systemic flaws. This approach hinders a thorough understanding of the event. By focusing solely on individuals or considering it a random occurrence, the underlying organizational, technical, and human factors contributing to the mishap are disregarded. 

This analysis was done as part of the "Human Factors and Systems" module at Loughborough University during my Masters in Ergonomics and Human Factors.

On April 10, 2015, a serious accident occurred at West Wickham station in South London. A passenger was dragged along the platform by a departing train when her backpack strap became trapped in the closing doors. As the train moved, she fell onto the platform and then through the gap between the platform and the train, resulting in life-changing injuries. 

The accident occurred during a Southeastern service from London Cannon Street to Hayes (Kent). The train was being driven by a trainee driver under the supervision of an instructor, and it was operating as a driver-only service. The Rail Accident Investigation Branch (RAIB) conducted an investigation which formed the basis for this analysis.



Understanding the root causes and contributing factors that lead to such accidents.


Enhance safety by identifying systemic vulnerabilities.


Developing targeted measures to mitigate the risk of similar accidents in the future.

Research & Analysis

To identify the root cause(s) that led to the Trap and Drag accident, a closer look into the whole system that operated is warranted. A systems-based technique for accident analysis is thus selected.


The Accimap method is selected as it is widely used in accident investigations that occur in complex sociotechnical systems. This is due to its basis in Rasmussen's risk management framework, its effectiveness in identifying contributory factors in potential systemic accidents, and its relatively more straightforward and easier-to-grasp nature compared to other advanced techniques such as HFACS and STAMP.

The RAIB accident report (dated 03/2016) was studied and all direct and indirect factors responsible for the occurrence of this event were then listed.

The Key Players are then identified in the listed factors. These Key players include Railway Authorities, workers and drivers and the individuals harmed in the incident.

The listed attributes are then grouped based on the level of significance and contribution towards the mishap. Based on the action and the reaction that ensued, three groups -

/ Causal factors

/ Contributory factors

/ Probable factors

The grouped factors are further clustered based on the identified key players involved per factor.  The clusters are then identified as Levels - External Level, Organisational Level, Workplace Level, Individual levels and finally the resulting Outcomes.

External Level includes indirect contributory factors including footfall at the Station on the day of the accident, an Individual's inculcated habit and their reflexes that could cause more harm than good.

Organisation Level includes the Higher level Organisations directly and indirectly involved in the incident - Southeastern Railway and Network Rail, the Railway Board and the Standards in place.

/ Workplace Level includes the specific train and platform where the incident occurred.

Individual Level includes the members directly involved in the incident - the passenger, the Driver and the Trainee Driver.

/ Outcomes Level includes the resulting outcomes listed in the investigation.

The Key Players are listed in rows and all identified factors are distributed across the board based on the key players involved in them. Connections are then made to identify the cause and the effects that followed. 

Trap and Drag AcciMap

Taking human factors into account is essential for developing effective preventive strategies and ensuring the safety of railway passengers. By analyzing the causal, contributing and probable factors on various levels, the following causes and their targeted interventions could then mitigate the risk of trap-and-drag incidents.

Factor - The owner and operator unaware of the train's door behaviour

Issue - Lack of effective communication between various stakeholders involved in the operation.

Intervention - Effective communication channels for system and infrastructure updates and enhanced training for trainee drivers and instructors on door operation and safety procedures, emphasizing the importance of ensuring passenger safety during boarding and alighting.


Factor - Service operated under a driver-only operation model which relies on the use of CCTV monitoring instead of physical checks of the doors

Issue - Lack of effective safety management processes in place to ensure that the risks associated with this operating model were properly identified and addressed.

Intervention - Conducting a systemic safety review to identify and address potential vulnerabilities in the train operation and dispatch process, with a focus on preventing similar incidents in the future.

Factor - The door operating system failed to re-open when the passenger's clothing was caught up in the gap

Issue - The door operating system only detects objects thicker than 30mm. Furthermore, upon detection of an obstruction, train doors partially reopen and re-shut with greater force.

​Intervention - Enhance the obstruction detection sensors by using more sensitive sensors, such as infrared or laser-based sensors to detect smaller obstructions. Evaluating and modifying door control systems to prevent unexpected and rapid door closure, particularly when passengers are alighting or boarding.

Factor - No Platform staff to assist with train dispatch

​Issue - Train Driver had increased responsibility of performing platform checks in addition to his work protocols. 

Intervention - Implement additional measures, such as improved platform monitoring systems and around-the-clock designated officers to ensure the safety of passengers during the boarding and alighting process.

​The key takeaway from this study is the systematic identification of active and latent failures within an organization, aiming to understand the underlying causal factors that lead to an accident. The study also aims to establish how these accidents can be prevented, emphasizing the importance of addressing systemic factors to improve safety and prevent similar incidents in the future.

GOV.UK. (n.d.). RAIB report 03/2016: Serious accident at West Wickham station. [online] Available at: [Accessed 3 Mar. 2023].

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