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22 C H A P T E R 4 Introduction This chapter describes the factors that impact safety at the rail transit platform/guideway and platform/vehicles interfaces. The factors that affect the horizontal and vertical gap distances include platform design, platform height from top of rail, and platform surface. Other factors include the track characteristics such as track infrastructure and geometry, curved and tangent track, guideway characteristics, shared use track, and trains bypassing stations. The vehicle char- acteristics include the type of door and the configuration of the train. Platform Design The platform design can be a significant factor that affects the frequency of incidents at platform/ guideway and platform/vehicle interfaces. Platform design takes into consideration whether the platform is a side platform or a center platform. The Tokyo University of Science study places an emphasis on station design and the specific impacts of design characteristics on safety (24). Two primary factors in the study were the overall area of the platform and the length of narrow or obstructed sections on the platform. Accord- ing to the study, the overall safety of the platform increased as the area or size of the platform increased. Conversely, as the length of the narrow sections of the platform increased the overall safety at the platform decreased. In general, larger platforms with more standing area are safer than those that are smaller. This study reported that island platforms and curved platforms were more dangerous than single sided and straight platforms (24). However, other literature reviewed did not show a consensus on whether island platforms or side platforms are safer. Advantages listed for island platforms include using less right of way, ease of transfer between tracks for passengers, shared facilities, and the need for fewer station attendants. One disadvantage of island platforms is the overcrowding resulting when two trains are located on either side of the platform at the same time, creating crossing passenger flows and overcrowding on stairs and escalators. Side plat- forms may offer more standing room and eliminate the problem of crossing passenger flows, but additional station staff and extra stairs, elevators, and escalators are required. Platform Height from Top of Rail The literature review and incident data analysis showed that platform height measured from top of rail impacts platform/guideway interface and passenger safety. There is a correlation between platform height and severity of injury (12). High height platforms that are 3 ft or higher Factors That Impact Safety at Rail Transit Platform/Guideway and Platform/Vehicle Interfaces
Factors That Impact Safety at Rail Transit Platform/Guideway and Platform/Vehicle Interfaces 23 from the top of rail have more reported incidents and often require significant treatments to improve safety. Heavy rail and commuter rail systems tend to have high height platforms. Light rail and streetcar transit often operate on low height platforms that are less than 15 in. from the top of rail. However, light rail and streetcar transit agencies did report that on low platforms people are more likely to enter the guideway and stand at the edge of the platform, which could result in passenger injuries. Table 4.1 contains the platform types and their corresponding rail transit modes. Table 4.2 contains the standard platform heights from top of rail for (a) select U.S. rail transit agencies, (b) the APTA streetcar, and (c) the UK standard. Figure 4.1 provides a graphic representation of the data in Table 4.2. The height of the platform may vary depending on the age of the line within a transit agency, and prevent vehicles from moving between different lines. Figure 4.2 shows a high height platform that serves the West Side Express commuter rail ser- vice operated by Tri-County Metropolitan Transportation District of Oregon (TRIMET) in the Table 4.1. Generalized platform types and rail transit modes. Generalized Platform Type1 Transit Mode1 Heavy Rail Commuter Light Rail and Streetcar High height (over 36 in. from top of rail) Mini-High (mixed height platforms with low level and higher level sections) Low (8 to 14 in. from top of rail; more common height is 14 in.) Very Low (less than 8 in. from top of rail) 1There are transit systems that operate hybrid type designs that do not fall into these categories. Table 4.2. Standard platform heights from top of rail for select U.S. systems, APTA streetcar, and the UK. Standard Platform Heights from Top of Rail Organization or Agency Platform Height United States in. mm NYC Subway A Division (IRT) 43 in. (1092.2 mm) for ADA Zones 42.375 1076.3 NYC Subway B Division (BMT/IND) 44 in. (1117.6 mm) for ADA Zones 42.375 1076.3 Boston MBTA Blue Line 41.5 1050 Boston Green Line 14 360 Philadelphia Southeastern Pennsylvania Transportation Authority (SEPTA) (select lines) 42.5 1080 Washington, DC, Washington Metropolitan Area Transit Authority (WMATA) 38.5 980 San Francisco Bay Area Rapid Transit (BART) 42 1100 LA Metro (select lines) 39 998 San Diego Trolley 8 205 APTA Streetcar Standard 14 360 Europe UK TSI Standard 35.7 915+ 0.25
24 Manual to Improve Rail Transit Safety at Platform/Vehicle and Platform/Guideway Interfaces Portland, Oregon, region. This photograph also shows the gauntlet track that moves the passen- ger trains closer to the platform edge. Mini-High Platforms Mini-high platforms are often used when there is a mix of high and low floor vehicles. The mini-high platform has two levels: a low height and a raised height area. These platforms are also used when a stop or station is shared by both bus and rail transit. In this situation, the light rail or streetcar vehicle will have accessible level boarding in the middle of the vehicle and require a step Figure 4.1. Chart of standard platform height for select transit agencies, APTA, and UK systems. 0 5 10 15 20 25 30 35 40 45 Plaorm Height Above Top of Rail H ei gh t ( In .) Figure 4.2. High level platformâWest Side Express (WES), Portland, Oregon.
Factors That Impact Safety at Rail Transit Platform/Guideway and Platform/Vehicle Interfaces 25 up into the vehicle at either end. The lower platform height located at one or both ends is used to access buses. Mini-high platforms have ramps between the low height and higher height levels. The only safety issues reported include passengers stepping directly into the guideway or using the platform edge as a bench. Figure 4.3 shows a mini-high platform for a streetcar operation. Low Platform Streetcars and light rail transit often use low or very low height platforms to achieve level or near level boarding. Low platforms generally are 14 in. from top of rail to platform surface while very low platforms are 8 in. or less from top of rail to platform level. Figure 4.4 shows a very low height platform with a designated pedestrian crossing area in the middle of the station. Platform Surface Platform surface materials are hard and durable. Platforms that are outdoors and exposed to the weather are made of concrete, asphalt, or brick pavers. Underground stations may have terrazzo, marble, or granite platform surfaces. The 24-in.-wide detectable warning at the plat- form edge is a requirement of the ADA and most often has truncated domes that are either (a) imprinted and painted concrete or (b) fiberglass or plastic materials that are bonded to the Figure 4.3. Mini-high platform (6). Figure 4.4. Very low height platform.
26 Manual to Improve Rail Transit Safety at Platform/Vehicle and Platform/Guideway Interfaces underlying platform material. Platforms that are cracked or have uneven surfaces can lead to tripping and falling incidents. Similar incidents are encountered when the edge of the platform is crumbling. An unstable edge can potentially lead to a platform/vehicle interface injury. Weather and Platform Surface Several studies have acknowledged the significance of weather conditions of platform safety. A report published by the RSSB examined the effects of weather on vehicle/platform interface incidents in the UK. According to this RSSB study, when the platform is wet or icy, there is an almost 5% increase in incidents. If the platform is both icy and wet, the rate of incidents increases by nearly 20%. The results from the study also predicted an increase in incidents during the winter months compared with the summer months (17). A study detailing safety issues on platforms on the Bangkok Mass Transit System also found through a passenger survey that people tend to be more careful when there is wind and rain present (20). Based on the results, it appears that inclement weather can have a significant effect on incidents on platforms that are exposed to the weather. Track Infrastructure and Geometry Rail transit track infrastructure can affect the safety at the platform/vehicle interface because of gaps. In general, rail transit operations are divided into two different categories: exclusive and shared use track. Exclusive track operations involve track and guideway that are reserved for a specific mode of rail transit. Exclusive track is frequently owned and maintained by the rail transit agency. Shared use track operations include track that is shared with freight trains or other rail transit modes. Commuter rail systems often share track with freight and, as a result, the station platforms need to be set back further from the track to comply with freight car clear- ance standards. Light rail and streetcar operations sometimes share platforms with each other and with buses. In these operations, platforms must be designed to accommodate level boarding for the various modes. The size of the horizontal and vertical gaps is often associated with platform/vehicle interface incidents. The ADA regulations for level boarding platforms recommend that the horizontal gap not exceed 3 in. and the vertical gap be less than 5â8 in. from platform to rail car. A boarding and alighting study conducted at Delft University of Technology determined that an increase in either the vertical or horizontal gap would lead to a corresponding decrease in capacity for that given door (4). Shared Use Track Some rail transit agencies operate on shared use track with freight rail. It is important to note that the width of a passenger rail car is generally narrower than the width of an average freight car. With state mandated side clearance standards based on the freight car width, this introduces an excessive horizontal gap between platform edge and passenger train car. Curved Track Curved track sections influence the safety at the platform/vehicle interface. There are two primary classifications for stations with curves: concave and convex. Concave curve. The cars at the ends of the vehicle are near the platform edge but the center car doors have a wide horizontal gap when a station is located on a concave or outside curve (17, 26).
Factors That Impact Safety at Rail Transit Platform/Guideway and Platform/Vehicle Interfaces 27 Convex curve. The cars in the middle section of the vehicle are near the platform edge, but the cars at the ends have a wide horizontal gap when a station is located on a convex or inside curve. The severity of the gap depends on the length of the vehicle and the degree of curve (11). On a curve, both the degree of curvature and associated superelevation impact the size of the gap. For every 1-degree of track curvature, an additional 1 in. of horizontal gap is required to ensure that the train cars do not strike the edge while passing. For a vertical gap, 1 in. of superelevation corresponds to an additional 1 in. of vertical gap. Figure 4.5 shows the impact of superelevation on gaps at the station platform (14). Guideway: Ballast and Direct Fixation Rail transit systems often use both ballasted and direct fixation track in the guideway. Ballasted track systems use wooden and concrete ties that are supported by aggregate ballast. Direct fixa- tion track consists of rails held in place with special rail fasteners that are anchored into concrete placed on the bottom of tunnels or on elevated rail structures. Rail transit modes that have direct fixation track do not normally have issues with track movement. Track shift with ballasted track can vary significantly based on a number of factors including, but not limited to, curvature, posted train speed of track, shared use corridor, frequency of use, and track conditions. However, there are many stations where traditional ballasted track is used in stations and along platforms. Regular measurement and maintenance is required to ensure that both vertical and horizontal gap dimensions are acceptable along the entire length of each platform. Platform/Vehicle Interface Characteristics Trains Bypassing Stations The FRA Approach to Managing Gap Safety describes factors of train operations that can affect gap safety. There are rail transit operations such as express service where trains bypass a Figure 4.5. Superelevation in relation to gap (14). Super Elevation
28 Manual to Improve Rail Transit Safety at Platform/Vehicle and Platform/Guideway Interfaces station at a high speed. In this case, the horizontal gaps need to be larger to ensure that the train does not strike the platform when bypassing a station (9). NYCT uses bypass tracks for trains that are express trains or trains that are skipping stations. Other transit agencies reduce the speed of trains when they are running through the station to minimize the chance of a train striking the platform edge. Since the enactment of the ADA regulations, the maximum horizontal gap has been regulated to no more than 3 in. Vehicle Characteristics Vehicle characteristics that relate to level boarding and the platform/vehicle interface include (a) vehicle doors and (b) train consists and train car coupling. Vehicle Doors The type of vehicle doors on rail transit vehicles is primarily determined by vehicle designers and transit agencies. The design of the vehicle door can affect both the horizontal and the ver- tical gap between the platform edge and the vehicle. The following are the three most popular door styles: Plug Doors. These doors âplugâ into the side of the vehicle when the doors close. This type of door does not take up internal vehicle space and permits a tight seal that reduces the wind enter- ing the cars and suppresses noise. One of the primary disadvantages of plug doors is that they swing out over the platform when opening and closing. This requires space between the vehicle and the platform and increases the horizontal gap, the vertical gap, or both between the car and the platform. The use of plug doors may impact level boarding. In general, when the platform is slightly lower than the vehicle floor the doors should operate correctly without impacting the platform. Plug doors are found on different modes of rail transit vehicles. Figure 4.6 shows plug doors on an OC Transpo vehicle. Folding Doors. These doors swing out over the platform and have the same impact on verti- cal and horizontal gaps as plug doors. Folding doors can have either two sections as on a transit Figure 4.6. Plug doors on an OC Transpo light rail car.
Factors That Impact Safety at Rail Transit Platform/Guideway and Platform/Vehicle Interfaces 29 bus, or two double sections that fold like an accordion when open. In either case, the doors gen- erally protrude over the platform when open, and this may impact platform space and interrupt passenger flows. The platform height must be lower than the door opening height and this affects the vertical gap tolerance. Folding doors are more common on older rail transit vehicles; recent vehicle procurements have not included folding doors. This type of door was on the Chicago Transit Authority 2200 Series Cars. Most of these cars have been retired. Sliding (Pocket) Doors. These doors are self-contained between the exterior and interior walls of the rail vehicle. Sliding doors permit tighter vertical gap tolerance and the floor of the vehicle is at the same level as the platform. These doors permit wide open door clearance and this directly influences boarding and alighting time. The sliding door can also influence the location of windows and other equipment near the door because of the space in the wall they require when opened. Sliding or pocket doors can also affect the seating capacity of a rail transit vehicle. Figure 4.7 shows the sliding door with an extended threshold and the closed sliding doors on the opposite side of the vestibule. Train Consists and Train Car Coupling Since the enactment of the ADA in 1990, most new rail transit systems are designed with level boarding. However, some of the older rail transit systems do not have level boarding on all vehicles. To overcome the vertical gaps, rail transit agencies may operate train consists that are a combination of older high floor vehicles and newer low floor vehicles. Consequently, some of the cars in a train consist may have a vertical gap and others may afford level boarding. Rail transit trains can be as short as a single car or as long as a 12-car consist. A train consist can be permanently coupled or changed throughout the day. The coupling between rail vehicles introduces a significant gap between the vehicles. Table 4.3 lists the typical number of cars per consist by transit mode. Some newer light rail and streetcar vehicles in Europe are âmarried,â Figure 4.7. Open sliding door with an extended threshold.
30 Manual to Improve Rail Transit Safety at Platform/Vehicle and Platform/Guideway Interfaces and are designed to be continuous with a longer configuration that cannot be uncoupled. This design eliminates the gap between vehicles, but the size of the train consist is permanent. Many heavy and commuter rail systems have trains that are more permanently coupled or married. However, there are transit operators that change the vehicle consist configuration daily for off peak and peak operations. The changes in configuration introduce operational factors that ultimately influence the space between vehicles. The between-car space on light rail and streetcar vehicles has been identified as a factor for platform/vehicle interface incidents. Table 4.3. Typical consist lengths based on rail transit mode. Generalized Vehicle Type Transit Mode Heavy Rail Commuter Light Rail and Streetcars Multi-car trains: 6 or more cars 4 to 6 cars 1 to 4 cars
