Train door systems are associated with a high number of passenger injuries and are typically the source of the greatest number of incidents that cause train operating delays. In this article, Rail Systems Expert Steve Noonan provides an overview of the design and operational aspects of train doors as they relate to injuries and other mishaps.
Passenger Train Doors - Expert Article
Doors are a primary interface between passengers and trains. Passengers navigate entries, exits, and riding with trains in a variety of ways. These systems typically work as intended, but malfunctions do occur and can result in minor to catastrophic injuries.
In mass transit applications, such as subway or light rail trains, side doors are typically used to provide direct access to the passenger compartment. This arrangement allows for the rapid exit and entry required for large passenger flows with tight schedules, but also creates a very dynamic condition with associated risks. Even after passengers have entered the train, defects in operation (either automatic or operator initiated functions), can subject passengers to additional risks. An unintended door opening exposes passengers to a dangerous condition regardless of whether or not the train is in motion.
In commuter and intercity trains, a significant proportion of designs feature a two door entry/exit process. In these arrangements, passengers enter and exit from platforms through side doors to end of car vestibules. They enter and exit the passenger compartment through the vestibule end doors. End (or vestibule doors) can be power operated or manually operated. Each of these methods can introduce different potential injury modes as passengers navigate in and out of trains.
Train Door Safety Features
Modern train door systems incorporate various safety features that affect the forces, speed and (opening or closing) direction of door movement that can directly impact passengers. Due to the potential hazard severity associated with malfunctions, train doors are a frequent focus for operators and maintenance personnel including inspectors, repair technicians and engineers once they are in service. Certain features of the door systems are applied by designers with the intent of safeguarding the users within the context of a robust system that must sustain frequent use on a daily basis.
- Pushback Features – Door panels are fitted with pushback features that provide some level of buffering when the door comes into contact with a passenger or other object when closing.
- Re-cycling Features – Some doors have re-cycling features where a sensitive edge (or other types of) control devices reverse the direction of movement when an obstruction (such as a person’s arm in the door) is sensed.
- Selective (or Independent) Door Controllers – Door control systems sometimes have the capacity to enable the operator to isolate certain doors or groups of doors on a train. While offering useful options for the methods of operating doors on a train, they introduce complexities into the design. Simpler designs are inherently less susceptible to failures, having fewer elements/devices to fail that can lead to operating system failures.
- Interlocking Devices – When equipped and set to operate in a normal mode, interlocking devices inhibit the activation of train propulsion such that if doors do not achieve a “closed and locked” status, the train cannot proceed.
These features provide protection to passengers and are incorporated into a control system to provide assurance the doors are closed and locked before the train proceeds to the next stop/station. Balancing the objective for efficient operation of passenger doors with the need for safety is initially the burden of the system designer. Designs must comply with minimum industry standards, and must be analyzed from a System Safety perspective that applies specific methods of engineering analysis contained in recognized national and international standards.
Design, Testing, and Controls
The components and devices that control the doors must meet rigorous standards of reliability with proven, quantifiable histories of reliable performance. Designs are validated through rigorous testing of the first article of a specific door system application to a train car. The “first article” is essentially a prototype of the final design produced by the manufacturer of the system. Based on its performance in testing, the design is either validated or revised before validating. This testing is performed under controlled conditions in an instrumented laboratory type setting and then again in the first train produced in a project during its commissioning for service. Properly maintained door systems are subjected to routine inspection and maintenance protocols to ensure that they continue to operate as designed.
In addition to the design and maintenance elements of the door systems, operational controls are put in place for conductors, engineers, and motormen to delay or stop the train altogether if there is an issue developing at the doors or on the platform. Operational controls are either pushbutton style panels where the operators can manually initiate opening and closing of doors, or by preset door operating cycles tied to a train’s positioning in a station. When door design features and operational controls work as intended, injuries and other mishaps can be averted.
FORENSIC INVESTIGATIONS INVOLVING TRAIN DOORS
Forensic investigations involving the function or operation of train doors, will typically examine design documents, maintenance records, and operational procedures. Experts specializing in the design and operation of rail systems can frequently determine the factors that contributed to the cause of each incident.
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Rail Systems & Mechanical Engineering Expert
Steve Noonan is a railroad systems expert with specialized expertise in rail vehicles, equipment, and facilities. He has more than 40 years of engineering experience relevant to the safety and reliability of regional networks, light rail systems, subways, and monorails. Steve applies his expertise to forensic casework involving economic loss claims and personal injury disputes.