Patent Publication Number: US-6340268-B1

Title: Impact attenuating barrier wall

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to guardrail systems extending along a roadway, such as a conventional highway or a race track, for redirecting an errant vehicle back onto the roadway. It is especially directed to a novel, impact attenuating compressible barrier wall system capable of redirecting an errant vehicle back onto the roadway with minimal decelerating effect, minimal damage to the vehicle, and reduced risk of injury to the driver. 
     Roadways are often lined with protective barriers such as concrete walls and/or fixed guardrails including standard metal W-beams. When a car strikes against a concrete wall or an unyielding guardrail, even at a shallow angle the car can experience significant deceleration and damage and the driver can be seriously injured. 
     One prior effort to deal with these problems has been the placement of bundles of tires tied together and stacked in front of fixed obstacles such as the concrete barriers and unyielding guardrails. However, when hit at a shallow angle at high speeds, the tire walls can snag the car and violently reject it back into the stream of traffic, creating a dangerous situation for all drivers. 
     Another proposed places longitudinally extending vehicle interfacing rails adjacent the roadway and resilient energy absorbing cylinders between the rails and the fixed obstacles. Upon impact, the rails move with the car, absorbing energy and reducing damage to the car. This proposal works very well, preventing snagging and, after impact, restoring the rails substantially to their original operative position. 
     The invention described herein is considered to be an improvement over this latter proposal in that it eliminates the interfacing rails and relies only on a novel arrangement of resilient energy absorbing cylinders to absorb the energy of an impacting errant vehicle and to redirect the vehicle back onto the roadway. 
     SUMMARY OF THE INVENTION 
     Accordingly, the primary object of this invention is to provide an impact attenuating barrier wall extending along a roadway, the wall including a novel arrangement of resilient energy absorbing cylinders which, upon impact by an errant car, effectively intercept and redirect the car back onto the roadway with minimal damage to the car and reduced risk of injury to the driver. 
     The novel barrier wall of the invention achieves its objectives by providing a plurality of large diameter, compressible, resilient energy absorbing cylinders positioned in side-by-side relationship along the roadway between the roadway and an outer fixed protective barrier or obstacle such as a longitudinally extending concrete wall on a standard fixed guardrail. Gaps are formed between the inner halves of the side-by-side cylinders adjacent the roadway, and smaller diameter cylinders are placed in those gaps to substantially fill those gaps. Upon initial impact by an errant vehicle, the inner halves of the larger and smaller cylinders are compressed to form a substantially continuous vertical surface intercepting the vehicle, absorbing the energy of the vehicle and reducing damage to the vehicle. Placing the smaller cylinders in the gaps prevents snagging, and the cylinders effectively redirect the vehicle back into the roadway. 
     The cylinders are preferably constructed of a high molecular weight/high density (HMW/HD) polyethylene material of the type disclosed in U.S. Pat. No. 5,403,112, and possess the unique ability to first dissipate large amounts of energy upon impact by a vehicle, and then restore themselves to about 90 percent of their original shape, thereby substantially maintaining the integrity of the barrier wall through repeated impacts. 
     Other objects and advantages will become apparent from reading the following detailed description of the invention wherein reference is made to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of the impact attenuating barrier wall of the invention; 
     FIG. 2 is a top perspective view of the barrier wall of the invention; 
     FIG. 3 is a top plan view of the invention; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, the impact attenuating barrier wall  10  of the invention extends longitudinal along the side of a roadway  12  on which vehicles are traveling in the direction of arrow  14 . 
     Barrier wall  10  includes a standard fixed protective barrier or obstacle such as a concrete wall  16  or a conventional W-beam guardrail system extending along the side of the roadway. 
     A plurality of large diameter compressible resilient energy absorbing cylinders  18  are arranged in side-by-side abutting relationship between roadway  12  and wall  16 . Each of the cylinders is fastened to wall  16  by a bolt and strap assembly  20 , and adjacent cylinders are fastened together by bolt and strap assemblies  22 . 
     As mentioned above, cylinders  18  are of HMW/HD polyethylene material capable of absorbing substantial energy as they are compressed by an impacting errant vehicle and of redirecting the vehicle back onto the roadway  12 . After impact, the cylinders slowly restore themselves substantially back to their original shape for continued use. 
     In a prototype of the invention, cylinders  18  were 36″ diameter×48″ high×1″ wall thickness. The cylinders are sized to normally accommodate various sized vehicles of different mass and different CG&#39;s e.g. CG&#39;s within the range of about 12≧24 inches covering Formula 1 race cars to standard passenger vehicles. 
     As viewed in FIGS. 2 and 3, as the inner halves  24  of cylinders  18  diverge from bolt assemblies  22  away from each other toward roadway  12  a gap or space  26  is defined between the inner halves of adjacent cylinders adjacent roadway  12 . Those gaps, if left exposed to roadway  12  and vehicles traveling thereon, may cause the inner halves  24  of cylinders  18  to snag an errant vehicle and perhaps violently reject it back into the stream of traffic on roadway  12 , thus creating a dangerous situation for all drivers. 
     To alleviate that potential problem, a smaller diameter HMW/HD polyethylene cylinder (8″ diameter×48″ high×½″ wall in the prototype) is positioned in each of gaps  26  and fastened against adjacent halves  24  by bolt/strap assemblies  32 . As viewed in FIG. 3, cylinders  30  close the gaps  26 , and the inner edges  32  and  34  of cylinders  18  and  30  lie in substantially the same vertical plane  40  extending along roadway  12 . 
     When struck at a shallow angle by an errant vehicle, cylinders  18  and  30  collapse or flatten upon themselves and together form a slightly interrupted but substantially continuous vertical impact surface engaging the vehicle, absorbing the energy of the vehicle, and safely redirecting the vehicle back onto roadway with reduced damage to the vehicle. After impact, cylinders  18  and  30  slowly return substantially to their original shapes, thus restoring and maintaining the integrity of barrier wall  10  to its original condition for use in attenuating additional impacts. 
     As an additional safety measure, at the upstreams end of barrier wall  10  are a series of cylinders  42 ,  44 ,  46  increasing in diameter to the first cylinder  18  as a lead into the main wall section. In the prototype, cylinders  42 ,  44  and  46  were 8″,18″, and 24″ diameter, respectively, all with ½″ wall thickness. These cylinders avoid any abrupt head on impact at the upstream end. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.