Platform-to-Railcar Gap (Mind the Gap*)
By Carl Berkowitz, Ph.D., PE, AICP
cmberkowitz@hotmail.com
This article addresses two critical safety issues that affect passengers using subway and commuter rail platforms: platform-to-railcar horizontal gap and platform-to-railcar vertical gap.
The National Safety Council ranks falling second only to automobile injuries as the nation’s leading accident cause. All pedestrian falls begin with a slip or a trip and must be taken seriously, as they can result in potentially fatal injuries or permanent disabilities. Therefore rail- passenger providers must exercise the highest degree of care in reducing or eliminating the causes of falls associated with their operations. Rail passenger gap falls occur when an object or the nature of the walking surface prevents or delays the passenger’s rear leg from moving forward to achieve a safe footing at the instant the foot makes contact with the surface ahead. Safe walking requires perfect timing in the transfer of support and balance from one leg to the other. The slightest change can result in an imbalance that can result in a serious fall as the body continues to move forward.
There are two aspects to the platform gap: the vertical difference between the car floor and platform surface elevation and the horizontal separation of the railcar from the platform. Today’s rail transit equipment uses mechanical and automatic car floor leveling systems to maintain the car floor nearly level with the passenger platform. This is an important safety feature because when the railcar floor is above the platform, it creates a tripping hazard for passengers boarding the vehicle; when the car floor is below the passenger platform, it is a tripping hazard for passengers exiting the railcar. Most falls are initially precipitated by a trip, and if the gap is wide enough, extension of the passenger’s leg might fall into the space.
Most modern transit systems, with proper design and construction of platforms, together with proper maintenance and proper car floor leveling devices, can attain safe vertical and horizontal gap clearances. This makes it unlikely that a passenger will trip on the car doorsill or platform, or that a passenger’s foot will pass between the car and the platform. It is clearly recognized by the rail passenger industry that the gap between a passenger railcar and the passenger platform is a critical interface where dangerous passenger falls can occur.
The U.S. Department of Transportation’s Accessibility Handbook for Transit Facilities (1992) addresses the various standards for rail platforms, including relationship to vehicle gaps, and access to vehicles from platforms using lifts and ramps. This handbook recommends:
The New York City Transit Station Planning Guidelines recommend that the IRT System be 4 feet 4.75 inches from the centerline of the car to the edge of the car and 4 feet 8.25 inches from the center line of the car to the wood edge (rub rail); IND/BMT Divisions should be 5 feet from the center line of the car to the edge of the car and 5 feet 2 inches from the centerline of the car to the wood edge (rub rail). The standard for horizontal gap is 2 inches for the IND and BMT divisions and 3 to 3.5 inches (depends on width of rubbing board) for the IRT Division. The three divisions use a specially designed load leveling system to achieve proper car-platform alignment to eliminate any vertical gap.
Tripping hazards are determined by the clearance of the foot during walking. Foot clearances during walking have been observed to range from 0.375 inches to 1.5 inches (average 0.6 inches). The American National Standards Institute requires that the height differentials in adjacent surfaces of more 0.25 inches be beveled and more than 0.5-inch clearance be ramped. This standard is consistent with observed foot clearances and the recognition that height differentials of 0.5 inches or greater are tripping hazards.
The Architectural and Transportation Barriers Compliance Board has developed rail transit platform gap requirements for commuter rail systems as part of the Americans with Disabilities Act (ADA). This Act has exceptions for existing commuter railroad facilities and equipment, which temporarily exempt older systems from full compliance; however, it should be noted that the ADA standards were developed through an open public hearing process. This process included comments and recommendations by the rail passenger industry, including rail transit. The resulting standards are considered fully representative of the current state-of-the-art and are now the common standards of practice for designing rail transit systems. These standards require a horizontal gap of no greater than 3 inches and a vertical difference within plus or minus 1.5 inches under normal passenger load conditions. (Federal Register, Rules and Regulations, Vol. 56, No. 173, September 6, 1991, pp. 45521-45524.)
The horizontal and vertical gap between the platform and the railcar presents a potential risk for someone to trip and fall. Passengers have limited control over preventing gap type injuries. The rail operator has to exercise due care to reduce this risk by better managing and eventually eliminating the defects in the design of the platform (following ADA, APTA and FRA guidelines).
* Phrase used by the London Transport.
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