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Direct Fixation Fasteners: Bringing the PATH Tunnels into the 21st Century

January 2003

Almost one hundred years after the original construction, the rehabilitation taking place in PATH Tunnels 'E" and 'F' under the Hudson River does not look much different than it did in 1908 when the tunnels were first being built. After completely removing all of the water damaged equipment from the tunnels so that only the 16'-wide cast iron tunnel ring liners remained (still intact after nearly a century of use), workers set about restoring all of the previous systems. This work included replacement of the tunnel trackwork, duct banks, cables, lighting, drainage, fire protection, communications and railroad signals. While the materials were upgraded to bring the specifications up to current codes and industry standards (for example, fiber reinforced epoxy conduit replaced the old clay ducts and steel reinforced concrete duct banks replaced the original, severely deteriorated duct banks), the configuration of the new systems is strikingly similar to the original design. Much of the labor is even being done manually, because the confined space and limited access in the tunnels precludes the use of large modern machinery.

One element that has changed significantly however is the replacement of the original wooden tie and ballast track bed system. In the original design, the running rail was fastened to evenly spaced wooden crossties that were embedded in a layer of ballast (stone gravel) for stability. In the current reconstruction, a series of direct fixation fasteners will be used instead to secure the rail to the track bed. These direct fixation fasteners are composed of a steel baseplate with rail seat and baseplate pads, side insulators, rail clips, and threaded anchor bolts. They are attached at even intervals to the rail and then bolted to the concrete track bed, eliminating the need for wooden crossties or a ballast layer. The innovative design of the direct fixation fasteners allows for some thermal expansion and contraction of the continuously welded rails, while keeping them securely in place. This is the first such application of the direct fixation method used by PATH.

There are many clear advantages to the use of the direct fixation fastener system. Because of the elimination of the wooden cross ties and ballast layer, there are significant savings in track maintenance, electrical insulation, load distribution and longevity. In addition, trains running on tracks using the direct fixation system will sway less and work more efficiently in the narrow, century-old tunnels.

For passengers, the benefits of a change to a direct fixation fastener system will include a smoother and quieter ride when service is restored between the Exchange Place and World Trade Center PATH stations in 2003.

 
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