Railway Track & Structures - October 2008 - (Page 14)

AREMA NEWS for motorcycles and other two-wheeled vehicles. The proposed system substantially reduces both these difficulties. In these situations, the raised barrier would normally face highway traffic at an angle, so the vehicle, if it impacts the barrier, would tend to slide to one side. This would reduce impact forces somewhat. If it was feared that vehicles might resultingly pass around the barrier and foul the railroad right-ofway, a secondary, fixed barrier could be installed at right angles to the highway or adjacent to the roadway. The highway can extend across the railroad without any perceptible deviation in the highway surface. Highway crowning can be maintained through the Railroad Highway Crossing without change. The highway and associated sidewalk, if any, is closed when a train passes, so no train warning horn is required. This can be an advantage in built-up residential areas sensitive to noises. The Railroad Highway Crossing can be especially effective in allowing “no train horn” regulations to be put in place. This can be particularly useful in municipalities and localities where antirailroad “not in my backyard” agitation is especially active. The Railroad Highway Crossing is an effective, economical substitute for full grade separation in congested areas where such grade separation is inconvenient due to conflict with local businesses, cross streets, traffic signals, etc. There may be locations where busy roads cross railroad tracks such as in densely populated urban areas, where difficulties with adjacent property access, street intersections adjacent to the railroad, or other reasons make complete grade separation impractical or prohibitively expensive, making the Railroad Highway Crossing the proper choice. The Railroad Highway Crossing may also be no more expensive to install or maintain than other solutions for “no train horn” sites. Impact absorbing capability can be built into the Railroad Highway Crossing to minimize damage to highway vehicles and reduce the likelihood of injury to occupants. This capability can be designed so that no damage normally occurs to the gate/crossing in the event of an impact by a highway vehicle. This can avoid costly repairs or delays in the 14 Railway Track & Structures October 2008 event of a collision. The Railroad Highway Crossing can also be used for other types of rail systems such as magnetic levitation systems or for third-rail-powered rail lines. Any configuration of railroad or transportation system can be accommodated by the Railroad Highway Crossing. Disadvantages This system provides some inconvenience to highway travelers, in the form of delays due to train traffic and requires some maintenance and operation expense on the part of the railroad. It is not recommended as a replacement for all existing highway-railroad grade crossings. Busy, high-speed highways would usually be better served by having complete grade separations constructed. With the Railroad Highway Crossing, a second mechanical device somewhat more complicated than crossing arms must be maintained. The roadway deck over the track is movable and may be 20 or 30 or more feet wide and 100 feet long or more. This must be pivoted up and down each time a train is to pass. The hinges must be kept in good condition, and the points on which the gate/crossing rests when lowered must be kept in proper contact when the gate/crossing is in position to carry highway traffic. In most cases, standard crossing gate arms should be retained, to act as warning gates ahead of the barrier/roadway. The warning gates should be operated sequentially so that they are fully lowered and blocking traffic before the gate/crossing is raised. This will increase the total time that the highway is closed during passage of a train. The presence or entry of persons or vehicles onto the crossing when the barrier is about to be raised cannot be entirely prevented. Similar situations have arisen with movable bridges that are remotely operated or do not provide the bridge operator with a clear view of the roadway. These difficulties have generally been adequately surmounted. Configuration The Railroad Highway Crossing would consist of a movable deck, typically formed of open grating, over the tracks. The deck would be hinged where it meets the approach roadway. Ordinarily, two separate sections would be provided, one hinged to the approach on one side of the tracks, and one on the other. These two sections would meet along the centerline of the railroad. The Railroad Highway Crossing sections can be constructed of any material, in any configuration, so long as they are capable of supporting the traffic. AASHTO (The American Association of State Highway and Transportation Officials) provides applicable standards for design of the highway portion of a crossing. Typically, a separate activating mechanism would power each section up and down. As the moving sections would be relatively light in weight, no counterweighting mechanism would be provided, unless a reduction in gate operating force requirements was deemed necessary, say in remote areas where limited power is available. At highways separated by a median strip, separate Railroad Highway Crossing installations can be made for each separate highway section. For systems crossing a single track railroad line, the moving sections could rest when lowered directly on the railroad rails, with cushioning and load distribution to avoid misalignment of the track. For multiple track railroad crossings, independent pedestals can be provided to support the free ends of the moving highway sections in the lowered position. Where crossing two or more tracks, hinges can be placed in the gate/crossing sections so that they fold as the Railroad Highway Crossing raises, reducing the height of the raised gate/crossing, minimizing the effect of high winds on the gate/crossing, and reducing the amount of power required for operation. Where two or more tracks are widely separated, independent Railroad Highway Crossings can be installed at each track. The Railroad Highway Crossing can be asymmetrical, so that, for instance, if crossing three tracks, one section can span across one track, while the other section spans two tracks. Additional supports could be placed between the center track and the other track, supporting the larger section at its midpoint. The larger section could be designed to fold if desired. The joint of the folding sections in this case would meet between tracks where rigid pedestal supports would support them. www.rtands.com http://www.arema.org http://www.rtands.com

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Railway Track & Structures - October 2008

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