Easy on, easy off

On many passenger rail systems, the Bridge and Building (B&B) Department is an important part of an effective track production program, keeping heavy track production units moving forward. Work on high-level and low-level passenger platforms falls under the responsibility of B&B.

On high density passenger rail systems with three or more main line tracks, such as Amtrak and Metro-North, great consideration must be given to supporting loading and unloading of passengers in stations during track production. This task usually involves some sort of station platform modification and is traditionally given to B&B. Safe and efficient boarding of passengers while production equipment is in a station’s track block is important for customer loyalty.

At one time, the Northeast Corridor and many other main lines had mostly low-level platforms for commuter stops and high-level platforms at major cities only. Since the early 1980s, many of the low-level platforms have been converted to high level for efficient passenger loading and unloading. This greatly improved station dwell time and travel time. However, this situation brought rise to the issue of getting passengers safely from a high level platform to a train on an “inside track” in the event of an extended track outage on an “outside” track. Many new railcars are only partially equipped for low-level platform boarding with traps (SEPTA), and some are not equipped to allow for low-level boarding at all (Amtrak Acela Express, LIRR).

Traditional methods

The traditional method of moving passengers to inner tracks in the event of an outer track being out of service has been timber platforms at the track level that run out into the center tracks. This practice still exists and is used mainly for unplanned outages such as a broken down train or short-duration track maintenance. Another method of passenger transfer is the Boni Car, a flat car outfitted with higher-elevation decking so that passengers on a high-level platform can walk across the flat car sitting on the outer track and board a train on an inner track. This method is efficient but costly to construct and maintain. The aluminum bridge plate is a narrow aluminum scaffolding with one set of legs set into the ballast for stability. The other end is anchored into the high-level platform. Each unit must by slung by a hi-rail crane, walked to its desired location while slung and set into place, then lagged to the platform. Setup is time consuming and difficult. Also, the constrained width makes it difficult for a train crew to spot a train in the precise location required to line the doors with the bridge plate. In short, there is no standard scaffolding—each installation is designed for a particular station and is only used once.

Mobile Passenger Scaffolding

To facilitate the best features of each aforementioned temporary platform system, a small group of engineers and a veteran B&B Supervisor at Amtrak were assembled and tasked. The requirements were to have a bridge plate called a Mobile Passenger Scaffolding (MPS) that could be slung by a small rail crane or off-road fork lift and be pushed by the force of two people on the rail into place, thus negating the need of a train crew and locomotive. Also, the units would have to be completely installed in a 48-hour period to bridge across track with a platform length of 1,100 feet. The structure had to meet AREMA loading requirements.

Once requirements were established, the team designed a mock-up that was built and tested by Amtrak’s New York Division B&B Department. The purpose of the mock-up was to validate the maximum dimension and weight that the B&B Department equipment and work force could safely and efficiently maneuver under catenary wires near an operating railroad. After a successful mock-up was tested and analyzed, the detailed design and fabrication of two working prototypes was commissioned. The prototype contract was awarded to a steel fabrication shop from Pennsylvania in close proximity to the job site location. This helped to facilitate a team effort.

As a result of the mock-up, the team determined that the structure would need to move both laterally and vertically to accommodate mildly varying track centers and track elevations across the Northeast Corridor main line with respect to the permanent concrete high-level platforms. Also, as a result of creating the mock-up, it was determined that the MPS would have to overlap the existing concrete platforms with a small cantilever. The cantilever concept eliminated any wide-gap conditions due to wide track centers by permitting the MPS to be pre-adjusted toward the train as necessary. The small cantilever also eliminated any gap between the MPS and the concrete platform.

Designing lateral and vertical adjustment capability involved making each MPS a two-section unit. The first section is a steel chassis structure with wheels attached for rolling and a vertical screw jack at each corner for vertical adjustment. The second section is an aluminum top plate that can be pulled or pushed laterally by hand in a fashion perpendicular to the rail or train to allow for the gap to be minimized with deviating track alignments. The top plate sits in a track on the chassis and is locked into the required location by large pins. Each unit is numbered.

The method of fixing and holding an MPS in place is a U-shaped bolt with large wing nuts. The bolt secures the chassis of the MPS to the rails—two per chassis and one on each rail. The system requires at least one weekly B&B Department inspection to check for signs of movement and loose fasteners.

Handrail spacing is at a specified length perpendicular to the train to assist in passenger safety and prevent passengers from running alongside the train. Also, the railing serves to eliminate any tripping hazard between any adjacent MPS unit. Therefore, handrail spacing is intended to correspond with the length of each unit.

Accommodating multiple car types

Ultimately, MPS unit length and handrail spacing was determined by the requirement to accommodate door spacing on multiple types of equipment: Amtrak Amfleet Coaches, NJT Arrow III EMUs with center doors, NJT Comet coaches with and without center doors, and NJT Multi-Levels with multiple end doors. As a result, railing spacing would need to alternate between 10 feet and 20 feet so that every door on every train could open. The team selected 10 feet unit lengths to standardize the design. Where 20-foot sections are required, two 10-foot sections would be bolted together.

An additional feature is that this system can be used as individual units for revenue train service as opposed to one continuous-length platform. For example, if only six train doors are required to open at a low-density station, then six MPSs will be set out as individual units at those doors.

The total time for installation for an 1,100-foot platform is approximately 30 hours and requires a work force of ten plus watchmen. Breakdown takes the same amount of time. Also important is mobilization; MPSs can be loaded and moved by highway to job site or loaded onto flat cars and moved by rail.

An important aspect of the MPS is the efficiency and safety of the installation process. Also significant is the convenience for passengers to board trains safely, and train crews to facilitate that task efficiently.