Patent Publication Number: US-7220077-B2

Title: Traffic noise barrier system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application No. 60/559,738 filed Apr. 6, 2004 and entitled “Traffic Noise Barrier System”, which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to traffic noise barriers. More specifically, this invention relates to a crashworthy traffic noise barrier system for bridge rails and other longitudinal barriers. 
     2. Description of the Related Art 
     Traffic noise barrier walls serve to shield otherwise quiet areas from noise caused by automotive, railway, aircraft, marine, or pedestrian traffic. A typical traffic noise barrier wall is from about 4 to 24 feet in height and runs continuously alongside a selected section of a roadway, railway, aircraft runway, waterway, parking lot, walkway, and the like. 
     One common design of a traffic noise barrier wall includes a plurality of panels of wood or concrete supported by vertically mounted posts. Examples of such noise barrier walls are found in U.S. Pat. Nos. 5,713,170 and 5,537,788, both issued to Elmore et al. Noise barrier walls of this type are suitably sturdy and effective in reducing highway noise; however, such noise barrier walls are usually not designed for vehicle impact. As a result, these noise barriers are located many feet (e.g., 40 feet) from the normal path of traffic. Problematically, space constraints often require that noise barriers be located closer to the path of traffic. One example is when a noise barrier is required on a bridge. 
     Where space constraints exist, it is not uncommon for noise barriers to be mounted on top of a crashworthy traffic barrier. One example of such an arrangement is found in U.S. Pat. No. 4,214,411 issued to Pickett, wherein panels of transparent material are secured between beams mounted on top of a roadside barrier. The transparent panels are effective in providing travelers on the traffic path with a view outside the roadway. However, vehicles impacting the otherwise crashworthy traffic barrier may also strike the noise barrier, creating potential hazards to the impacting vehicle and nearby pedestrians. 
     The U.S. Federal Highway Administration (FHWA) requires all longitudinal barriers used on the National Highway System (NHS) to be crashworthy and to qualify as such according to the testing and acceptance guidelines of the National Cooperative Highway Research Program (NCHRP) Report No. 350, which is incorporated by reference herein in its entirety. Under NCHRP Report No. 350, longitudinal barriers include any device whose primary functions are to prevent vehicular penetration and to safely redirect an errant vehicle away from a hazard outside the normal path of the vehicle (e.g., outside the roadway). Longitudinal barriers include, for example, roadside barriers, median barriers, and bridge rails. For longitudinal barriers, NCHRP Report No. 350 defines six test levels, each of which prescribe test conditions appropriate for a range of highway types, traffic volumes, and other parameters. Test Level 1 (TL-1) and Test Level 2 (TL-2) are intended for low-speed and/or low-volume roads, while Test Level 3 (TL-3) through Test Level 6 (TL-6) are intended for high-speed facilities with increasingly higher traffic volumes. TL-1, TL-2, and TL-3 require redirection of an 820-kg car impacting a barrier at 20 degrees, and a 2,000-kg pickup truck impacting a barrier at 25 degrees, at speeds of 50 km/h, 70 km/h, and 100 km/h, respectively. TL-4 adds an 8,000-kg single-unit truck at 15 degrees and 80 km/h to the TL-3 matrix; TL-5 substitutes a 36,000-kg tractor/van trailer for the single-unit truck. TL-6 substitutes a 36,000-kg tractor/tank trailer. Thus, to be used on the NHS, a longitudinal barrier must be accepted by the FHWA as meeting one or more test levels of NCHRP 350. Such acceptance is typically indicated in a letter from the FHWA to the manufacturer of the longitudinal barrier or in a published memo from the FHWA. 
     Although NCHRP Report No. 350 offers guidance for the safety performance evaluation of longitudinal and other traffic barriers, it offers no guidance toward the evaluation of attachments on or near these barriers. Some guidance toward the evaluation of barrier attachments to barriers is provided in a technical paper entitled “Guidelines for Attachments to Bridge Rails and Median Barriers” by Keller et al. Using the Test Levels outlined in NCHRP Report No. 350, Keller et al. identify a “Zone of Intrusion” (ZOI) for a wide variety of traffic barriers, including sloped-face concrete parapets (e.g., New Jersey, Single Slope, F-shape, and open concrete rail), vertical-faced concrete parapets (e.g., vertical wall and open concrete rail), steel corrugated rails (e.g., W-beam and thrie beam), steel tubular rails, steel tubular rails on curbs, combination concrete and steel tube railings, and timber bridge rails. The ZOI represents an envelope around the barrier into which various vehicular components intrude upon the vehicle&#39;s impact with the barrier. 
     For noise barriers and similar attachments, referred to by Keller et al. as “continuous attachments”, Keller et al. provide various design considerations that allow such attachments to be placed in the ZOI. One suggestion is to use attachments that will breakaway, allowing the system to deflect upon impact by a vehicle. Where non-breakaway attachments are used, Keller et al. suggest that the design take into account the snag potential of the attachment. Snagging is when a portion of a vehicle engages a vertical element, such as a post, causing deceleration of the vehicle. In addition to snagging concerns, Keller et al. suggest that the potential implications of debris from impacts on these systems be considered because debris associated with the attachment may fall on traffic and/or pedestrians around or below the barrier. Keller et al. also suggest that vehicle occupant compartment intrusion and deformation be considered. Occupant compartment intrusion and deformation is a concern for traffic barrier attachments under two scenarios: (1) a vehicle component is driven into the occupant compartment due to impact with the attachment; or (2) the attachment itself intrudes into or deforms the occupant compartment. While Keller et al. provide various guidelines for the design of barrier attachments, Keller et al. fail to provide a design for a traffic noise barrier wall that would meet their guidelines. 
     Thus, there is a need for a traffic noise barrier wall for use where space constraints require the noise barrier wall to be located near a selected section of a roadway, railway, aircraft runway, waterway, parking lot, walkway, and the like, and which will prevent vehicle deceleration due to snagging, will reduce or eliminate occupant compartment intrusion and deformation, and which will reduce or eliminate falling debris concerns. 
     BRIEF SUMMARY OF THE INVENTION 
     The above-described and other needs are met by a traffic noise barrier system for use alongside a path of traffic. The traffic noise barrier system comprises a longitudinal barrier extending substantially parallel to the path of traffic, and a traffic noise barrier wall supported by the longitudinal barrier. The traffic noise barrier wall includes: a plurality of upstanding posts attached to the traffic noise barrier wall; a plurality of panels supported by the plurality of upstanding posts; and at least one longitudinal beam extending across the plurality of upstanding posts for redirecting a portion of an errant vehicle away from the plurality of panels. The at least one longitudinal beam may include a first longitudinal beam spaced above the longitudinal barrier and disposed between the path of traffic and the plurality of panels, and a second longitudinal beam spaced above the first longitudinal beam and disposed between the path of traffic and the plurality of panels. 
     The panels may be disposed between each pair of adjacent posts. One or more of the panels may be transparent, and one or more of the panels may be reinforced with plastic bands, plastic threads, or a plastic net. The plastic threads may be high-contrast plastic threads, the high-contrast plastic threads having sufficient contrast to be recognized by birds flying in the vicinity of the panel and causing no substantial impairment of the overall transparency of the panel. Each panel in the plurality of panels may have a rigid frame disposed around at least a portion of its perimeter. 
     A rear support beam may be disposed on an opposite side of the panel from the first longitudinal beam, and a front support beam may be attached to the first longitudinal beam, between the first longitudinal beam and the panel Resilient members may be disposed between the front support beam and the panel and between the rear support beam and the panel. The longitudinal beam may be formed from a plurality of axially aligned sections. 
     A horizontal centerline of the first longitudinal beam is preferably spaced a distance between about 32 inches to about 44 inches above a terrain surface, and more preferably at 38 inches above the terrain surface. A horizontal centerline of the second longitudinal beam is preferably spaced a distance between about 44 inches to about 74 inches above the terrain surface, and more preferably 60 inches above the terrain surface. The longitudinal barrier may be qualified under National Cooperative Highway Research Program Report No. 350 Test Level 3. 
     In another embodiment, a third longitudinal beam is disposed between the path of traffic and the plurality of panels. The third longitudinal beam extends across the plurality of upstanding posts and is spaced above the second longitudinal beam. A horizontal centerline of the third longitudinal beam is preferably spaced a distance between about 100 inches to about 154 inches above the terrain surface, and more preferably about 128 inches above the terrain surface. The longitudinal barrier may be qualified under National Cooperative Highway Research Program Report No. 350 Test Level 4. In one embodiment, the longitudinal barrier has a height greater than or equal to 40 inches above the terrain surface and the first longitudinal beam is omitted. 
     Each of the upstanding posts may have a flange extending along substantially an entire height of the upstanding post. The flange extends generally parallel to the panel and forms a gap between opposing, generally parallel surfaces of the flange and the panel. Preferably, the gap is less than or equal to about ½ inch. In one embodiment, an anti-intrusion wedge is disposed within the gap. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings wherein like elements are numbered alike, and in which: 
         FIG. 1  is a perspective view of a crashworthy traffic noise barrier system of the present invention; 
         FIG. 2  is a side elevation view of the crashworthy traffic noise barrier system; 
         FIG. 3  is a front elevation view of the crashworthy traffic noise barrier system; 
         FIG. 4  is a perspective view of a portion of a panel in the crashworthy traffic noise barrier system. 
         FIG. 5  is a perspective view of a portion of an alternative panel in the crashworthy traffic noise barrier system. 
         FIG. 6  is a plan view of longitudinal beams and upstanding posts showing a deflection of the longitudinal beam under a load applied normal to the longitudinal beam at a point mid span between the upstanding posts. 
         FIG. 7  is a rear elevation view of a post connected to a longitudinal barrier in the traffic noise barrier system; 
         FIG. 8  is a cross-sectional elevation view of the post connected to a longitudinal barrier in the traffic noise barrier system; 
         FIG. 9  is a plan view of an embodiment of the traffic noise barrier system including panel support features; 
         FIG. 10  is a cross-sectional plan view of a portion of a panel support frame; and 
         FIG. 11  is a cross-sectional plan view of an anti-intrusion wedge disposed between a post and a panel. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 3 , a traffic noise barrier system  10  for use alongside a path of traffic  12  is shown.  FIG. 1  is a perspective view of the system  10 ,  FIG. 2  is a side elevation view of the system  10 , and  FIG. 3  is front elevation view of the system  10 . The path of traffic  12  may be a roadway, railway, aircraft runway, waterway, parking lot, walkway, bridge and the like. The traffic noise barrier system  10  includes a longitudinal barrier  14  and a traffic noise barrier wall (noise wall)  16  supported by the longitudinal barrier  14 . The longitudinal barrier  14  may be any barrier extending longitudinally along at least a portion of the path of traffic  12 . For example, the longitudinal barrier  14  may include one or more parapets, median barriers, bridge railings, and the like. The longitudinal barrier  14  includes a front surface  18  facing the path of traffic  12 , a top surface  20  adjacent to the front surface  18 , and a back surface  22  opposite the front surface  18 . In the present embodiment, the traffic noise barrier wall  16  is attached to the back surface  22 . 
     The traffic noise barrier wall  16  includes spaced-apart, upstanding posts  24  having panels  26  extending between each pair of posts  24 . In the embodiment shown, one panel  26  is disposed between each pair of posts  24 , however, it is contemplated that one or more panels  26  may be disposed between each pair of posts  24 . The noise barrier wall  16  has a height above a terrain surface  28  of the path of traffic  12  that is appropriate for the particular application of the wall  16 . For example, the height of the noise barrier wall  16  may be from about 4 to 18 feet, depending on the noise abatement requirements of the wall  16 . 
     Each panel  26  is made from an acoustically absorptive and/or reflective material that is appropriate for the individual application of the traffic noise barrier wall  16 . For example, the panels  26  may be made of a transparent material where it is desired that travelers on the path of traffic  12  have a view through the wall  16 . One example of a preferred transparent material for use as a panel  26  is PARAGLAS SOUNDSTOP® Noise Barrier Sheet commercially available from CYRO Industries, 100 Enterprise Drive, Rockaway, N.J. Where transparency is not desired, other materials such as wood, steel, opaque acrylic, plastic, and the like, may be used. The panel  26  may be corrugated for added strength. 
     Referring to  FIG. 4 , the panel  26  may also be reinforced with threads, bands, a net, or the like, as indicated at  27 , which in the event that the panel breaks, will hold the pieces of the panel  26  together. Noise Barrier Sheet panels reinforced with threads are commercially available from the aforementioned CYRO Industries. For example, one or more of the panels  26  may be a transparent polymer panel having spaced parallel faces and containing plastic threads, plastic bands, or a plastic net embedded approximately midway between the parallel faces and extending parallel to the faces, as described in U.S. Pat. No. 5,040,352 issued Aug. 20, 1991 to Oberlander et al., which is incorporated by reference herein in its entirety. As shown in  FIG. 4 , the embedded plastic threads or bands  27  may run parallel to each other in one direction.  FIG. 5  depicts an alternative panel  26  wherein the plastic threads or bands  27  run parallel to each other in two directions. It will be appreciated that the embodiment of  FIG. 5  may be accomplished using a net. 
     Referring to  FIG. 4 , the panel  26  may be a cast acrylic glass panel  29  in which plastic threads are embedded. The plastic threads  27  are parallel to each other and are approximately midway between the faces of the panel  26 . Alternatively, referring to  FIG. 5 , the panel  26  can be manufactured using two acrylic glass panels  31  connected to one another by an intermediate layer  33 . The plastic threads  27  are embedded in the intermediate layer  33  approximately in the middle. The intermediate layer  33  may be formed from a cold-hardening methacrylate resin. 
     Where the panels  26  include plastic threads  27 , these threads  27  may be high-contrast so that they can be recognized by birds flying in the vicinity of the panel while causing no substantial impairment of the overall transparency of the panel  26 , as described in U.S. Pat. No. 5,372,866 issued Dec. 13, 1994 to Oberlander et al., which is incorporated by reference herein in its entirety. The term “high contrast”, as used herein, refers to plastic which has a transmission ratio between 0 and 65% (measured according to DIN 5033 (colorimetry) and 5036 (radiometric and photometric properties of materials)). Preferably, the material or the actual plastic thread  27  has a transmission ratio of 0 to 30%, more particularly 0 to 10%. A transmission ratio of about 0% is particularly advantageous. To obtain contrast also, the plastic thread  27  must stand out from the background, e.g., by having a different color. Metal-coated threads are unsuitable for this purpose if, for example, they reflect the sky in front of the panel against the sky behind the panel or give undesired reflexes or reflections, e.g. of the sun. It is advantageous to use dark threads, particularly black threads. Owing to the high-contrast of the threads, flying birds can recognize the transparent panel  26  as an obstacle before they fly into it, and while they are a few meters away, and can fly around the panel  26 . 
     In particularly advantageous embodiments, the plastic threads  27  are 1 mm to 5 mm thick. More particularly the thickness range from 1.8 to 3.0 mm, preferably 2.0 to 2.5 mm, has been found particularly advantageous with regard to the required properties, i.e. easy insertion into the panel  26 , sufficient strength in the event of a fracture, sufficient visibility to birds and no substantial impairment of the overall transparency of the panel  26 . 
     The threads  27  in the panel  26  may extend horizontally, since the panels  26  are clamped at their sides; in that case the cohesion in the event of a fracture is particularly advantageous. The threads  27  may be laid parallel to one another. If desired or necessary, two layers of threads  27  can be incorporated in the panel  26  and will then preferably extend in two directions, an angle of 90° between threads  27  of different layers being particularly advantageous. 
     Usually, the distance between neighboring threads  27  is not greater than 100 mm, since greater distances markedly decreases the protection of birds or the prevention of fragmentation. Preferably, the distance between threads  27  is up to 50 mm, particularly when the threads  27  are horizontal, since birds appear to recognize horizontal obstacles less easily than vertical obstacles. 
     The surface density of the threads  27 , i.e. the percentage of the surface of the entire panel  26  which is covered by the threads  27  (the surface density), is usually from about 2.5 to about 25%. Preferably, particularly in the case of horizontal threads  27 , the surface density is at least about 5%, particularly advantageously about 6 to about 10%. In the case of vertical threads  27 , the surface density can be slightly less, so that, in this case, the advantageous range is from 5 to 8%. Below this surface density, the bird-protecting effect is rapidly lost, whereas above these values the threads  27  remain visible at a greater distance and detract from the appearance, i.e. the advantageous transparency of the plastic panel  26  is largely wasted. 
     Typical panel  26  thicknesses are preferably about 4 to about 40 millimeters, and more preferably 12 to 25 mm. The panels  26  are usually manufactured in sizes of 2×2.5 meters to 2×5 meters. Larger or smaller sizes are possible for special uses. 
     The panels  26  are usually substantially transparent, preferably colorless or slightly tinted, e.g. smoky brown. Colorless transparent plastic panels  26  usually have a transmission ratio of at least 70%. A ratio of about 90 to about 95% is advantageous. Tinted embodiments usually have a transmission ratio of about 45 to about 75%, for example between about 50 and about 60%. The absorption of the threads  27  and of the tinted panel  26  is cumulative, so that the threads  27  are additionally recognizable as high-contrast elements. 
     In the embodiments of  FIGS. 1-3 , the longitudinal barrier  14  is shown as a slope-faced concrete parapet commonly known as a Jersey barrier. It is contemplated, however, that any known kind of barrier may be used, including other sloped-face concrete parapets (e.g., Single Slope, F-shape, and open concrete rail), vertical-faced concrete parapets (e.g., vertical wall and open concrete rail), steel corrugated rails (e.g., W-beam and thrie beam), steel tubular rails, steel tubular rails on curbs, combination concrete and steel tube railings, and timber bridge rails. 
     Extending across the posts  24  are one or more longitudinal beams  32 ,  34  and  36 . The longitudinal beams  32 ,  34  and  36  extend generally parallel to the top surface  20  of the longitudinal barrier  14  and generally perpendicular to the upstanding posts  24 . In the embodiment shown, the posts  24  are formed from steel I-beams and longitudinal beams  32  are formed from steel tubes, respectively. It will be appreciated, however, that other rigid materials or structures may also be used. For example, the beams  32  or posts  24  may be formed from other metals (e.g., aluminum), fiberglass, and the like, and may be formed from a composite of materials. The beams  32  or posts  24  may be of any convenient cross sectional shape, such as for example: rounded (e.g., oval, ovoid, or round), I-beams, H-beams, channel beams, substantially flat, polygonal (e.g., triangular, quadrilateral (e.g., square, rectangular), pentagonal, hexagonal, heptagonal, octagonal, etc.). 
     The longitudinal beams  32 ,  34  and  36  are configured to redirect portions of an errant vehicle that may intrude into the area above the top surface  20  of the longitudinal barrier away from the panels  26 . The longitudinal beams  32 ,  34 , and  36  redirect energy of the errant vehicle away from the panels  26  such that the panels  26  and any fragments of the panels, remain attached to the traffic noise barrier wall  16 . As shown in  FIG. 2 , the horizontal centerline of the first beam  32  is spaced a distance y 1  from the terrain surface  28 , the horizontal centerline of the second beam  34  is spaced a distance y 2  from the terrain surface  28 , and the horizontal centerline of the third beam  36  is spaced a distance y 3  from the terrain surface  28 . Preferably, y 1  is between about 32 inches to about 44 inches and more preferably at about 38 inches. Preferably, y 2  is between about 44 inches to about 74 inches and more preferably at about 60 inches. Preferably, y 3  is between about 100 inches to about 154 inches and more preferably at about 128 inches. 
     The heights of y 1 , y 2  and y 3  are selected so that the corresponding longitudinal beams  32 ,  34  and  36  will impact different portions of an errant vehicle intruding into the area above the top surface  20  of the longitudinal barrier. Beam  32  is positioned at the height y 1  to contact the lower portion (e.g., hood and upper fender) of the vehicle (e.g., a single-unit truck for TL-4 and a ¾ ton pickup truck for TL-3), beam  34  is positioned at the height y 2  to contact the occupant compartment of the vehicle, and beam  36  is positioned at y 3  to contact a box portion of a vehicle such as a single-unit truck. Where the height of the traffic noise barrier wall  16  is less than that required to achieve this spacing (e.g., less than about 100 inches), the distances y 1  and y 2  are preferably maintained within the ranges provided, and the third beam  36  is placed at or near the top of the noise barrier wall  16 . 
     Referring to  FIG. 6 , the beams  32 ,  34  and  36  and posts  24  are designed to withstand, without breakage, a force F, which corresponds to the characteristics of traffic (e.g., speed of traffic, size of vehicles, number of vehicles, etc.) that will travel along the path of traffic  12 . It has been determined that in applications requiring the system  10  to be qualified under Test Level 4 of the NCHRP Report 350 and where the beams  32 ,  34 , and  36  are formed from steel, the first longitudinal beam  32  may be sized to deflect no more than about ½ inch under a force of 25 kips (1 kip=1000 pounds) applied in a direction away from the path of traffic and normal to the first longitudinal beam  32  at a point mid span (L/2) between two adjacent upstanding posts  24 . The second longitudinal beam  34  may be sized to deflect no more than about ½ inch under a force of 15 kips applied in a direction away from the path of traffic  12  and normal to the second longitudinal beam  34  at a point mid span (L/2) between the two adjacent upstanding posts  24 ; and the third longitudinal beam may be sized to deflect no more than about ½ inch under a force of 15 kips applied in a direction away from the path of traffic  12  and normal to the third longitudinal beam  36  at a point mid span (L/2) between the two adjacent upstanding posts  24 . It has been determined that by minimizing the deflection δ under these forces, the potential for breakage of the panels  26  and the potential for the errant vehicle snagging a post  24  are reduced. While no more than about ½ inch deflection δ for each of the beams  32 ,  34 , and  36  under their respective loads is preferred, it is believed that deflections δ of between about ¼ inch to about 6 inches under these loads are acceptable. 
     In any case, the force F and deflection δ to which the one or more beams (e.g.,  32 ,  34 , and/or  36 ) are designed are chosen to ensure that the longitudinal beams withstand an impact of 55 kips, which is typical of a collision caused by an 8000 kg single unit truck striking at an angle of 15 degrees relative to a line parallel to the barrier. Withstanding a collision with an 8000 kg single unit truck is a requirement of NCHRP Report 350 Test Level 4. It is contemplated that the one or more longitudinal beams may be of any shape, configuration or material that meets this design requirement. It is also contemplated that the beams  32 ,  34 ,  36  could be replaced with multiple beams in approximately the same locations so long as, together, they meet the same requirements. As previously noted, each beam  32 ,  34 ,  36  is designed to deflect either a certain part of a vehicle or a certain type of vehicle. For instance, the first beam  32  is designed to contact the lower portion (e.g., hood and upper fender) of a single-unit box truck, the second beam  34  is designed to contact the occupant compartment of the single-unit box truck, and the third beam  36  is designed to capture the top portion of the container of the single-unit box truck. This then dictates the height of the beams  32 ,  34 ,  36  and load capability that the beams  32 ,  34 , and  36  must withstand. It is also contemplated that different forces F and deflections δ can be incorporated into the design to meet other test criteria. 
     Also in applications requiring the system  10  to be qualified under Test Level 4 of the NCHRP Report No. 350, the upstanding posts  24  are preferably designed to withstand a load of 55 kips, applied as 25 kips on the first beam  32  and 15 kips each on the second and third beams  34 ,  36 , without separating from the longitudinal barrier  14  and without fracturing the upstanding posts  24 . 
     In applications requiring the system  10  to be qualified under Test Level 3 of the NCHRP Report No. 350, it has been determined that only the first and second beams  32  and  34  are needed and the third beam  36 , may be removed. It has also been determined that in applications requiring the system  10  be qualified under Test Level 3 of the NCHRP Report No. 350 and where the beams  32  and  34  are formed from steel, the first longitudinal beam  32  may be sized to deflect no more than about ½ inch under a force of 10 kips applied in a direction away from the path of traffic  12  and normal to the first longitudinal beam  32  at a point mid span (L/2) between two adjacent upstanding posts  24 ; and the second longitudinal beam  34  may be sized to deflect no more than about ½ inch under a force of 10 kips applied in a direction away from the path of traffic  12  and normal to the second longitudinal beam  34  at a point mid span (L/2) between the two adjacent upstanding posts  24 . It has been determined that by minimizing the deflection δ under these forces, the potential for breakage of the panels  26  and the potential for the errant vehicle snagging a post  24  are reduced. While no more than about ½ inch deflection δ for each of the beams  32  and  34  under their respective loads is preferred, it is believed that deflections δ of between about ¼ inch to about 6 inches under these loads are acceptable. 
     In any case, the force F and deflection δ to which the one or more beams (e.g.,  32  and/or  34 ) are designed are chosen to ensure that the longitudinal beams withstand an impact of 10 kips, which is typical of a collision caused by ¾ ton pickup truck having a weight of 2000 kg at an angle of 25 degrees relative to a line parallel to the barrier. Withstanding a collision with a ¾ ton pickup truck having a weight of 2000 kg is a requirement of NCHRP Report 350 Test Level 3. It is contemplated that the one or more longitudinal beams may be of any shape, configuration or material that meets this design requirement. It is also contemplated that the beams  32 ,  34  could be replaced with multiple beams in approximately the same locations so long as, together, they meet the same requirements. As previously noted, each beam  32 ,  34  is designed to deflect either a certain part of a vehicle or a certain type of vehicle. For instance, the first beam  32  is designed to contact the lower portion (e.g., hood and upper fender) of a ¾ ton pickup truck, and the second beam  34  is designed to contact the occupant compartment of the ¾ ton pickup truck. This then dictates the height of the beams  32 ,  34  and load capability that the beams  32 ,  34  must withstand. It is also contemplated that different forces F and deflections δ can be incorporated into the design to meet other test criteria. 
     Also in applications requiring the system  10  to be qualified under Test Level 3 of the NCHRP Report No. 350, the upstanding posts  24  are preferably designed to withstand a load of 10 kips, without separating from the longitudinal barrier  14  and without fracturing the upstanding posts  24 . 
     Referring again to  FIGS. 1-3 , the configuration of longitudinal beams  32 ,  34  and  36  allow the noise barrier wall  16  to be positioned close to traffic (e.g., against the back surface  22  of the longitudinal barrier  14  as shown in  FIG. 2 ), while minimizing the possibility that the panels  26  will break due to impact by an errant vehicle and while preventing the snagging of the errant vehicle on the upstanding posts  24 . This is particularly advantageous in applications, such as on bridges and the like, where space for the noise barrier wall  16  is limited. It will be appreciated that where sufficient space behind the longitudinal barrier  14  is available, the noise barrier wall  16  may be spaced apart from the back surface  22  of the longitudinal barrier  14  as described in co-pending U.S. patent application Ser. No. 10/718,022, entitled “TRAFFIC NOISE BARRIER SYSTEM” and filed on 19 Nov. 2003, which is incorporated by reference herein in its entirety. 
     Referring to  FIGS. 7 and 8 , the upstanding posts  24  may be connected to the longitudinal barrier  14  using a bolted assembly  50 . In the bolted assembly  50 , plurality of bolts  52  are secured within the longitudinal barrier  14 . A free end of the bolts  52  extends outward from the back surface  22  of the longitudinal barrier  14  and through apertures disposed in a pair of plates  54 . The plates  54  extend coplanar with the back surface  22  of the longitudinal barrier  14 , and are secured to the longitudinal barrier  14  by way of washers and nuts, which are threaded to the free end of the bolts  52 . The upstanding post  24 , which is an I-beam in this embodiment, is secured to the plate  54  by welding or otherwise fastening to a flange portion  56  of the upstanding post  24 . A plurality of support members  57  extend outward from a web portion  60  of the upstanding post  24  to the plate  54 . The upstanding posts  24 , as well as the remainder of the noise barrier wall  16 , may be supported entirely by the longitudinal barrier  14 . That is, the longitudinal barrier  14  carries the entire weight of the noise barrier wall  16  such that the noise barrier wall  16  is suspended above ground. Alternatively, the noise barrier wall  16  may be supported in part by the longitudinal barrier  14 . For example, the ends of the posts  24  may rest on the ground, bridge structure, or the like, with the longitudinal barrier providing support to hold the noise barrier  14  wall  16  in an upright position. 
     As also shown in  FIGS. 7 and 8 , the longitudinal beam  32  may be secured to the upstanding post  24  by L-shaped brackets  60 , which are disposed on the top and bottom sides of the longitudinal beam  32 . In the embodiment shown, the L-shaped brackets  60  are welded or otherwise fastened to the upstanding posts  24 , and one or more bolts  62  are disposed through the L-shaped brackets  60  and the longitudinal beam  32  to secure the longitudinal beam  32  between the L-shaped brackets  60 . Longitudinal beams  34  and  36  (e.g.,  FIG. 1 ) may be secured to the upstanding posts  24  using the same arrangement. 
     Referring to  FIG. 3 , the length of the noise barrier wall may exceed the length of each section  70  of material (e.g., metal tube) used to form the longitudinal beam  32 ,  34  or  36 . In this case, the sections  70  of material forming each longitudinal beam  32 ,  34  or  36  are preferably axially aligned and joined in butt-to-butt fashion. This method of joining the sections  70  maintains a substantially planar face  68  along the longitudinal beam  32 ,  34  or  36  towards the path of traffic  12  and, as a result, reduces the possibility of an errant vehicle snagging a portion of the longitudinal beam  32 ,  34  or  36 . For example, adjacent sections  70  of the longitudinal beam  32 ,  34  or  36  may be joined by disposing a rigid insert  72  within the hollow ends of each section  70  and securing the rigid insert  72  to each section  70  by disposing bolts  74  through each section  70  and through the rigid insert  72 , as shown in  FIG. 3 . 
       FIGS. 9 and 10  provide a plan view of a portion of the noise barrier wall  16  showing a method of securing panels  26  between upstanding posts  24 . While  FIGS. 9 and 10  show one method of securing panels  26  between upstanding posts  24 , it will be appreciated that other methods may also be used. For example, panels  26  may be disposed between posts  24  as described in U.S. patent application Ser. No. 10/777,442 filed Feb. 12, 2004 and entitled “Panel Assembly for Traffic Noise Barrier Wall”, which is incorporated by reference herein in its entirety. 
     As shown in  FIG. 9 , side edges of the panels  26  are secured within channels  80 , which extend along the length of the posts  24 . Each channel  80  is formed between the first flange  56  of the I-beam post  24 , and a second flange  82 , which is secured to the web  60  of the I-beam. Each panel  26  is positioned proximate the first flange  56  of the post  24  to reduce a gap formed between opposing, generally parallel surfaces the first flange  56  and the panel  26 . Minimizing this gap reduces the potential for a portion of a vehicle from wedging in this gap as the vehicle strikes the panel  26  and post  24  during impact and, thereby, prevents vehicle snagging, excessive vehicle deceleration, and redirection of the vehicle. Preferably, the gap formed between the opposing, generally parallel surfaces the first flange  56  and the panel  26  is no greater than about ½ inch. 
     In addition to minimizing the gap formed between the opposing, generally parallel surfaces the first flange  56  and the panel  26 , or where the gap is greater than about ½ inch, an anti-intrusion wedge  59  may be disposed between the post  24  and the panel  26 , as shown in  FIG. 11 . The anti-intrusion wedge  59  is a wedge-shaped structure that extends substantially along the entire height of the post  24 , and fills the gap formed between the opposing, generally parallel surfaces the first flange  56  and the panel  26 . The anti-intrusion wedge  59  may be formed from a resilient material (e.g., Ethylene Propylene Diene Monomer (EPDM) strips, rubber strips, plastic strips, and the like). The anti-intrusion wedge  59  has a sloped face  61  that extends from the first flange  56  to the panel  26 , and may include a rigid plate  63  (e.g., a metal plate) adhered to the sloped face  61 . The anti-intrusion wedge  59  prevents a portion of a vehicle striking the post  24  and panel  26  from entering the gap formed between the opposing, generally parallel surfaces the first flange  56  and the panel  26 , and thereby prevents vehicle snagging, excessive vehicle deceleration, and redirection of the vehicle. 
     Referring again to  FIGS. 9 and 10 , disposed along the side edges of each panel  26  is a frame  84 , which has a generally U-shaped cross section. The frame  84  captures the side edges of the panel  26 , and preferably extends along the entire length of the side edge of the panel  26 . Optionally, the frame  84  captures the entire perimeter of the panel  26  to enhance rigidity of the panel  26 . A resilient gasket  86  may be disposed between the frame  84  and the panel  26 . 
     The portions of the frame  84  disposed on the side edges of the panel  26  are each attached to channel beams  88 , which have a generally C-shaped cross section. Support members  90  may be attached between the frame  84  and the channel beam  88  to enhance structural rigidity, as shown in  FIG. 10 . Each channel beam  88  includes flange portions  92 , which are arranged to extend either towards the panel  26 , as shown in  FIG. 11 , or away from the panel  26 , as shown in  FIG. 10 . The distance between the outer surfaces of the flange portions  92  is less than the distance between the inner surfaces of the flange portions  56  and  82  of the upstanding post  24 , allowing the channel beams  88  to be received in the channel  80  formed in the upstanding post  24 . Resilient gaskets  94  may be disposed between the channel beams  88  and the upstanding posts  24  to secure the channel beams  88 , and thus the frame  84  and panel  26 , between the upstanding posts  24 . 
     Referring to  FIG. 9 , attached to a side of any one or more of the longitudinal beams  32 ,  34 ,  36  facing the panel  26  is a front support beam  97 . The front support beam  97  extends generally parallel to the longitudinal beams  32 ,  34 , or  36  and bridges a gap between the longitudinal beam  32 ,  34 , or  36  and the panel  26 . In the embodiment shown, the front support beam  97  is formed by a rigid tube. In addition, a rear support beam  98  may be positioned on an opposite side of the panel  26  from any one or more of the longitudinal beams  32 ,  34 ,  36 , with the rear support beam  98  extending parallel to the associated longitudinal beam  32 ,  34  or  36 . In the embodiment shown, the rear support beam  98  includes a plurality of rigid tubes  100 , each being disposed between a pair of adjacent posts  24  and each having a face disposed proximate an associated panel  26 . The rigid tubes  100  on opposite sides of each post  24  are supported by a generally U-shaped plate  102 , which extends around the post  24 . The U-shaped plate  102  is attached to the post  24  by a generally L-shaped bracket  104 , which is secured to an outer surface of the flange  82  of the post  24 . The rear support beam  98  and the front support beam  97  support the panel  26  against various loads such as, for example, wind loads, to prevent bending of the panel  26  and dislodging of the panel  26  from the frame  84 . Where the rear support beam  98  and the front support beam  97  are formed from a rigid material, resilient members (e.g., Ethylene Propylene Diene Monomer (EPDM) strips, rubber strips, plastic strips, and the like) may be disposed between the panel  26  and the front and rear support beams  97 ,  98  to prevent the panel from contacting the rigid material forming the front and rear support beams  97 ,  98 . 
     The traffic noise barrier system  10  provides a traffic noise barrier wall  16  supported by a longitudinal barrier  14 , which can be located near a selected section of a roadway, railway, aircraft runway, waterway, parking lot, walkway, and the like. The longitudinal beams  32 ,  34  and  36  are configured to redirect portions of an errant vehicle that may intrude into the area above the top surface  20  of the longitudinal barrier away from the panels  26 . The longitudinal beams  32 ,  34 , and  36  redirect energy of the errant vehicle away from the panels  26  such that the panels  26  and any fragments of the panels, remain attached to the traffic noise barrier wall  16 . As a result, the longitudinal beams  32 ,  34  and  36  prevent debris that would otherwise present a hazard to the occupants of the vehicle, surrounding traffic, and/or pedestrians around or below the barrier. In addition, the longitudinal beams  32 ,  34  and  36  prevent an errant vehicle from snagging on the upstanding posts  24 . As a result, the noise barrier wall  16  may be positioned close to traffic, while reducing or eliminating the vehicle snagging, occupant compartment intrusion and deformation, and debris concerns associated with traffic noise barriers of the prior art. This is particularly advantageous in applications, such as on bridges and the like, where space for the noise barrier wall is limited. In addition, the traffic noise barrier system  10  allows the use of transparent panels  26 , which allow travelers on the path of traffic  12  to view businesses and scenery outside the path of traffic  12 . Also, the use of reinforced panels  26  helps to further ensure that the panels  26  will not become a debris hazard or vehicle intrusion hazard. 
     A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.