Abstract:
A safety barrier comprising is disclosed. The safety barrier comprises a plurality of posts spaced from each other and disposed adjacent to a roadway, each post having a cross section defined in part by a web and a pair of legs extending therefrom. Additionally, each post has one slot formed in the web of the post extending from an upper end of the post. A first cable and a second cable are releasably engaged with and supported by the posts and disposed within each slot between the respective legs of each post. A third cable and a fourth cable are each coupled to an exterior surface of the posts. The posts and the first, second, third and fourth cables cooperate to prevent a vehicle from leaving the roadway.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention is related to highway barriers and safety systems and more particularly to cable safety systems and associated posts. 
       BACKGROUND OF THE INVENTION 
       [0002]    Cable safety systems and cable barriers have been installed along edges of roadways and highways for many years. Cable safety systems and cable barriers have also been installed along medians between roadways and/or highways. Cable safety systems generally include one or more horizontal cables attached to support posts. For some applications cable safety systems and cable barriers may reduce damage to an impacting vehicle and/or injury to occupants of the impacting vehicle as compared with other types of highway safety systems and highway barriers. 
         [0003]    Cable safety systems are often designed and installed with three cables mounted horizontally on a plurality of generally vertical support posts. The number of cables may vary depending on various factors such as the type of vehicles using the associated roadway and the hazard which required installation of the cable safety system. The length of a cable safety system is generally determined based on the adjacent roadside hazard. Each cable is typically installed at a desired height relative to the ground and with a desired spacing between adjacent cables. Associated support posts are installed with desired horizontal spacing between adjacent posts. 
         [0004]    One recognized limitation of cable safety systems is excessive deflection of associated cables during vehicle impact. Deflection associated with a cable safety system may be larger than deflection of a convention W-beam guardrail when subjected to the same type of vehicle impact. Such deflection frequently determines maximum allowed spacing between adjacent posts for satisfactory performance of the cable safety system. Large deflection during a vehicle impact also increases the risk of the vehicle running over the cables and being exposed to the hazard which required installation of the cable safety system. 
         [0005]    From full scale crash testing and from real life experience, it has been determined that keeping the length of unsupported cables as short as possible will generally reduce deflection. The longer the distance between adjacent posts supporting associated cables, the larger the deflection will generally be during a vehicle impact. An increased number of posts (shorter post spacing) will generally decrease deflection. However, shorter spacing between posts affects total cost of a cable safety system, not only material, but also installation cost. 
         [0006]    High-speed films from full-scale crash testing of vehicles with cable safety systems demonstrate that posts installed immediately adjacent to the location of a vehicle impact with unsupported portions of the cables will bend and/or deform in response to forces placed on the posts by the cables. When a post is bent at an angle of about ten (10°) degrees from vertical, the upper cable of a typical three cable safety system will often slide out of its associated slot or hook and lose its retaining capabilities. After another couple of degrees of the post bending from vertical, the second cable will slide out of its associated slot or hook. Finally, the third cable will slide out of its associated slot or hook when the post is bent about twenty eight to thirty (28° to 30°) degrees from normal. When the cables are released from posts adjacent to the point of vehicle impact, deflection of the cables will increase significantly. 
         [0007]    Vertical spacing between cables, vertical spacing of the cables relative to the associated roadway and horizontal spacing between adjacent posts are preferably designed and selected to allow the resulting cable safety system to satisfactorily function during a vehicle impact. Desired vertical spacing between cables and vertical spacing of cables relative to the ground may be obtained in a number of ways by using spacers, hooks, straps or other devices. The number of times an installer has to go to each post is of major concern since this not only takes time, but more importantly, exposes installers to the risk of being injured by traffic. Additional care must be taken with respect to design and installation of cable safety systems adjacent to curves in a highway or roadway and adjacent to inclines or slopes. 
         [0008]    During the past several years, cable safety systems have been used as an alternative to traditional W-beam guardrail systems. These cable safety systems address some of the weaknesses of prior cable safety systems by using pre-stressed cables and/or reducing the spacing between adjacent posts to reduce deflection to an acceptable level. A consultant report “Dynamic Analysis of Cable Guardrail” issued in April 1994 by an ES-Consult in Denmark, established a model for which parameters affect performance and designing desired deflection of cable safety systems. 
       SUMMARY OF THE INVENTION 
       [0009]    In accordance with particular embodiments of the present disclosure, the disadvantages and problems associated with cable guardrail safety systems have been substantially reduced or eliminated. 
         [0010]    In accordance with particular embodiments of the present disclosure, a safety barrier comprises a plurality of posts spaced from each other and disposed adjacent to a roadway, each post having a cross section defined in part by a web and a pair of legs extending therefrom. Additionally, each post has one slot formed in the web of the post extending from an upper end of the post. The safety barrier further comprises a first cable and a second cable releasably engaged with and supported by the posts and disposed within each slot between the respective legs of each post. The safety barrier further comprises a third cable and a fourth cable each coupled to an exterior surface of the posts. Each slot has a first edge and a second edge with respective sloping surfaces operable to slid ably receive the first cable and the second cable therein. The sloping surfaces on the first edge of each slot provide a first projection and the sloping surfaces on the second edge of each slot provide a second projection. The posts and the first, second, third and fourth cables cooperate to prevent a vehicle from leaving the roadway. 
         [0011]    In accordance with another embodiment of the present disclosure, a post for installing a cable safety system comprises a cross section defined in part by a web and a pair of legs extending from the web. The post also comprises a first end and a second end with a slot formed in the web starting at the first end an extending partially along the length of the post, the second end configured to be installed adjacent to a roadway. The slot has a first edge and a second edge and is sized to receive a first cable and a second cable therein. The post further comprises at least one restriction defined in part by respective sloping surfaces formed on each edge of the slot to increase retention time of the first cable and the second cable within the slot as the post is bent from a generally vertical position during a vehicle impact with the cables disposed within the slot. The post also comprises a first fastener coupled to a first exterior surface of the post, the first fastener size to receive a third cable and a second fastener coupled to a second exterior surface of the post, the second fastener sized to receive a fourth cable. The post also comprises at least one spacer disposed within the cross section of the post operable to maintain the cables at a desired spacing within the slot. 
         [0012]    In accordance with yet another embodiment of the present disclosure, a method of installed a cable safety system comprises forming a plurality of posts with each post having a slot extending from an upper end of the post. The method also includes forming the slot with a first edge and a second edge. Additionally, the method includes forming respective tapered surfaces on the first edge to provide a first projection and forming respective tapered surfaces on the second edge to provide a second projection. The method also includes forming at least one restriction within each slot defined in part by the first projection extending from the first edge and the second projection extending from the second edge to increase retention of the cables within the slot as the respective posts are bent from a generally vertical position. The method further includes installing the plurality of posts spaced from each other proximate to the roadway. The method further includes releasably engaging a first cable and a second cable within the respective slot formed in each of the posts and coupling a third cable and a fourth cable to an exterior surface of the posts. 
         [0013]    In accordance with yet another embodiment of the present disclosure, a method for manufacturing a support post for a cable safety system comprises forming a post with a first end and second end. The method also includes forming the post with a cross section defined in part by a web and a pair of legs extending therefrom. The method also includes forming a slot in the web extending from the first end of the post and forming the slot with a first edge and second edge. The method further includes forming respective tapered surfaces on the first edge to provide a first projection and respective tapered surfaces on the second edge to provide a second projection, the first projection extending from the first edge and the second projection extending from the second edge to increase retention of a first cable and a second cable in the slot as the post bends from a generally vertical position during a vehicle impact with the cable safety system. The method also includes forming at least one spacer disposed within the cross section of the post operable to maintain at least a first cable and a second cable at a desired spacing within the slot. 
         [0014]    Technical advantages provided by particular embodiments of the present disclosure include providing a cable safety system that maintains engagement between posts and associated cables for a longer period of time as the posts are bent from a generally vertical position during a vehicle impact. A cable safety system incorporating teachings of the present invention also minimizes the number of times an installer has to go to each post to position associated cables at desired heights relative to each other and an adjacent roadway. The present invention reduces both the cost and the time required to install a cable safety system. 
         [0015]    Technical advantages provided by particular embodiments of the present disclosure further include enabling cables and a metal portion of a support post to interact more quickly. This enables vehicles be more effectively redirected away from away from hazardous areas by enabling cables to provide resistance to vehicles impacting cable safety system sooner after impact. 
         [0016]    Moreover, because of the innovative support post, a support post may be manufactured at a reduced cost compared with previous designs. In particular, the inclusion of four cables in cable safety system allows for a shorter overall height of support post. The inclusion of an additional cable connected to the support post at an appropriate height enables the top-most cable to be positioned higher relative to ground level than previous systems. A higher overall cable height enables a support post to be shorter overall. Additionally, the inclusion of four cables allows for the use of a thinner web in support post. Further, a cable safety system may be manufactured without punching holes in the bottom of support post, which may substantially reduces the manufacturing cost of support post. 
         [0017]    In combination with four cables and other aspects of cable safety system, the smaller and thinner size of support post is effective to improve redirection of vehicles away from hazardous areas without causing serious injuries to the vehicle&#39;s occupants or other motorists. A smaller post in combination with a three-cable design would not have performed as effectively because a three-cable design may be less effective at preventing vehicles from summarizing or passing through cable safety system as compared to a four-cable design. A combination of a smaller and thinner support post may enable a support post to be manufactured at a weight of 5.7 pounds per foot, compared with a weight of 7.7 pounds per foot for previous designs, thereby enabling substantial cost savings during manufacture and maintenance. 
         [0018]    As a result, particular embodiments of the present disclosure may provide numerous technical advantages. Particular embodiments the present disclosure may provide some, none, all, or additional technical advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    A more complete and thorough understanding of the present invention and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
           [0020]      FIG. 1   a  is a schematic drawing in elevation with portions broken away of a cable safety system incorporating teachings of the present invention; 
           [0021]      FIG. 1   b  is a schematic drawing showing a plan view with portions broken away of the cable safety system of  FIG. 1   a;    
           [0022]      FIG. 1   c  is a schematic drawing in elevation with portions broken away of another cable safety system incorporating teachings of the present invention; 
           [0023]      FIG. 1   d  is a schematic drawing in section and in elevation with portions broken away of a below ground cable anchor assembly satisfactory for use with the cable safety system of  FIG. 1   c;    
           [0024]      FIG. 2  is a schematic drawing in section showing one example of a cable satisfactory for use in forming a cable safety system incorporating teachings of the present invention; 
           [0025]      FIG. 3  is a schematic drawing in elevation with portions broken away showing one example of a post and attached cables incorporating teachings of the present invention; 
           [0026]      FIG. 4  is a schematic drawing taken along lines  4 - 4  of  FIG. 3 ; 
           [0027]      FIG. 5  is an enlarged schematic drawing showing an isometric view with portions broken away of a post and cables incorporating teachings of the present invention; 
           [0028]      FIG. 6  is a schematic drawing showing an isometric view of one example of a spacer incorporating teachings of the present invention; 
           [0029]      FIG. 7  is a schematic drawing showing one method for installing the spacer of  FIG. 6  with the post and cables of  FIG. 5 ; 
           [0030]      FIG. 8   a  is a schematic drawing in section and in elevation showing one example of the results of a vehicle impacting a cable safety system; 
           [0031]      FIG. 8   b  is a schematic drawing in section and in elevation showing one example of the results of a vehicle impacting a cable safety system incorporating teachings of the present invention; 
           [0032]      FIG. 9  is a schematic drawing in elevation with portions broken away showing another example of a post formed in accordance with teachings of the present invention; 
           [0033]      FIGS. 10A-10I  are schematic drawings in section showing further examples of posts incorporating teachings of the present invention; 
           [0034]      FIG. 11  is a schematic drawing of a particular embodiment of cable safety system utilizing four cables; 
           [0035]      FIGS. 12B and 12B  is a schematic drawing showing a particular embodiment of a support post utilized in certain embodiments of a cable safety system; and 
           [0036]      FIGS. 13A and 13B  show schematic views of slots positioned in a support post, in accordance with particular embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    Preferred embodiments of the invention and its advantages are best understood by reference to  FIGS. 1A-13B  wherein like reference numbers indicate like features. 
         [0038]    The terms “safety system or systems” and “barrier or barriers” are used throughout this application to describe any type of safety system and/or barrier which may be formed in accordance with teachings of the present disclosure. The term “roadway” is used throughout this application to include any highway, roadway or path satisfactory for vehicle traffic. 
         [0039]    Various aspects of the present disclosure will be described with respect to cable safety system  20 . However, teachings of the present disclosure may be used to form a wide variety of cable safety systems and cable barriers. The present disclosure is not limited to cable safety system  20  as shown in  FIGS. 1   a - 1   d.    
         [0040]    Cable safety systems incorporating teachings of the present disclosure may be used in median strips or shoulders of highways, roadways or any other path which is likely to encounter vehicular traffic. The present disclosure may be used to form a wide variety of safety systems and barriers installed on a median between roadways and/or along the edge of a roadway. Cable safety system  20  may be installed adjacent to a roadway to prevent motor vehicles (not expressly shown) from leaving the roadway and to redirect vehicles away from hazardous areas without causing serious injuries to the vehicle&#39;s occupants or other motorists. The direction of traffic flow along the roadway is illustrated by directional arrow  22 . 
         [0041]    Cable safety system  20  preferably includes a plurality of support posts  30  anchored adjacent to the roadway. Posts  30  may be anchored with the ground using various techniques. The number, size, shape and configuration of posts  30  may be significantly modified within teachings of the present disclosure. A plurality of cables  60   a,    60   b  and  60   c  may be attached to support posts  30  in accordance with teachings of the present disclosure. Support posts  30  support and maintain associated cable  60   a,    60   b  and  60   c  in a substantially horizontal position extending along an edge of the roadway. The length of cables  60   a,    60   b  and  60   c  may be up to 3,000 meters between anchors  22  and  24 . For other applications the length of cable  60   a,    60   b  and  60   c  may exceed 3,000 meters without an intermediate anchorage. Support posts  30  also maintain desired vertical spacing between cables  60   a,    60   b  and  60   c  and desired vertical spacing of each cable relative to the ground. Cable safety system  20  including support posts  30  satisfy the criteria of CHIRP Report  350  including Level 3 requirements. 
         [0042]    Cable safety system  20  may be described as a flexible, substantially maintenance free system with designed low deflection of cables  60   a,    60   b,  and  60   c  during a vehicle impact. Support posts  30  preferably include a “rounded” and “soft” profile with cables  60   a,    60   b  and  60   c  placed within respective posts  30 . Forming cables safety system  20  in accordance with teachings of the present disclosure minimizes damage during a vehicle impact with cables  60   a,    60   b  and  60   c.  In some embodiments, cable safety system  20  includes three cables  60   a,    60   b  and  60   c  disposed in slot  40  of each post  30 . Cable  60   a,    60   b  and  60   c  are preferably disposed at different heights relative to the ground and relative to each other. Varying the vertical spacing between cables  60   a,    60   b  and  60   c  provides a much wider lateral catch area for vehicles impacting with cable safety system  20 . The vertical spacing between cables  60   a,    60   b  and  60   c  may be selected to satisfactorily contain both pickups and, to some extent, even larger vehicles with a relatively high center of gravity, as well as vehicles with a low front profile and low center of gravity. Cable safety system  20  may be satisfactorily used as a median, a single barrier installation along the edge of a roadway and at merge applications between adjacent roadways. For some applications cable safety system  20  may satisfactorily withstand a second impact before repairs have been made after a first impact. 
         [0043]    Various types of cables and/or wire ropes may be satisfactorily used to form a cable safety system in accordance with teachings of the present disclosure. Cables  60   a,    60   b  and  60   c  may be substantially identical. However, for some applications each cable of a cable safety system formed in accordance with teachings of the present disclosure may have different characteristics. 
         [0044]    Cables  60   a,    60   b  and  60   c  may be prefabricated in approximately three hundred (300) meter lengths with desired fittings (not expressly shown) attached with opposite ends of each cables  60   a,    60   b  and  60   c.  Tailor-made cables  60   a,    60   b  and  60   c  may then be delivered to a desired location for installation adjacent to a roadway. 
         [0045]    Alternatively, cables  60   a,    60   b,  and  60   c  may be formed from a single cable stored on a large drum (not expressly shown). Cables stored on drums may often exceed three thousand (3,000) meters in length. Cables  60   a,    60   b,  and  60   c  may be cut in desired lengths from the cable stored on the drum. Appropriate fittings (not expressly shown) may be swaged or otherwise attached with opposite ends of the respective cable  60   a,    60   b  and  60   c  at an onsite location. 
         [0046]    For some applications cable  60  may be formed from three groups of seven strands of wire rope. Cable  60  may have a modulus of elasticity of approximately 8,300 kg per square mm. The diameter of each strand used to form cable  60  may be approximately 3 mm. The diameter of cable  60  may be approximately 19 mm. Cables  60   a,    60   b  and  60   c  may be pre-stressed to approximately fifty percent (50%) of their designed or rated breaking strength. Cables  60   a,    60   b  and  60   c  may be installed between anchors  24  and  26  with approximately twenty thousand Neutrons of tension over a length of approximately three thousand (3,000) meters. 
         [0047]      FIG. 1   d  shows one example of a below ground anchor which may be satisfactorily used with a cable safety system incorporating teachings of the present invention. Respective holes  27  may be formed in the ground at desired locations for anchors  24   a  and  26   a.  A portion of each hole  27  may be filled with concrete foundation  28 . Anchor plate  29  may be securely engaged with concrete foundation  28  using various types of mechanical fasteners, including, but not limited to, a plurality of bolts  23  and nuts  24 . Anchor plate  29  may be formed at an appropriate angle to accommodate the design of cable safety system  20   a.  Also multiple slots and/or openings (not expressly shown) may be formed in anchor plate  29  to receive respective end fittings  64 . 
         [0048]    For the embodiment of the present invention as shown in  FIG. 1   d,  end fitting  64   a  of cable  160   a  is shown engaged with anchor plate  29 . Various types of anchor assemblies and cable end fittings may be satisfactorily used with a cable safety system incorporating teachings of the present invention. The present invention is not limited to anchor  24   a  or end fittings  64   a  as shown in  FIG. 1   d.    
         [0049]    One example of support posts  30  and cables  60   a,    60   b  and  60   c  which may be satisfactorily used to form cable safety system  20  in accordance with teachings of the present disclosure is shown in  FIGS. 3 ,  4  and  5 . Post  30  includes first end  31  and second end  32 . For this embodiment of the present disclosure, post  30  has a generally C-shaped cross section defined in part by web  34  with respective legs  35  and  36  extending therefrom. As best shown in  FIGS. 5 and 7 , the extreme edge of each leg  35  and  36  opposite from web  34  are preferably bent inward to eliminate any sharp edges. For some applications post  30  may be formed using roll forming techniques. For some applications second end  32  may be installed in a concrete foundation or footing  100  such as shown in  FIGS. 8   a  and  8   b . Alternatively second end  32  may be inserted directly into the ground. One or more soil plates (not expressly shown) may be attached to post  30  proximate second end  32  when post  30  is installed directly into the ground adjacent to a roadway. 
         [0050]    Slot  40  is preferably formed in web  34  extending from first end  31  towards second end  32 . The length of slot  40  is selected in part based on the desired vertical spacing of cable  60   c  relative to the adjacent roadway. The length of slot  40  is also selected to accommodate the number of cables which will be installed therein and desired vertical spacing between each cable. Slot  40  may have a generally elongated U-shaped configuration defined in part by first edge  41 , second edge  42  and bottom  43 . For the embodiment of the present disclosure as shown in  FIGS. 3-5 , first edge  41  and second edge  42  have a generally smooth profile and extend generally parallel with each other. In some embodiments, forming slot  40  within web  34  of post  30  may eliminate bolts, hooks or other mechanical attachments formed on the exterior thereof. 
         [0051]    For some applications post  30  may be formed from metal sheet having a thickness of 4 mm, a length varying approximately from 700 mm to 1,600 mm, and a width of approximately 350 mm. The metal sheet may weigh approximately 7.8 kg per meter. For other applications post  30  may be formed from a metal sheet having a thickness of 4 mm, a length varying approximately from 700 mm to 1,600 mm, a width of approximately 310 mm and a weight of less 4.5 kg per meter. Post  30  may be installed adjacent to a roadway by either driving directly into the soil adjacent to the roadway or by placing end  32  of post  30  in a concrete foundation. See  FIGS. 8   a  and  8   b . For other applications a foot plate (not expressly shown) may be attached to second end  32  of post  30  for use in bolting or otherwise securely attaching post  30  with a larger foot plate (not expressly shown) cast into a concrete foundation or similar structure adjacent to a roadway. 
         [0052]    For some applications cap  50  may be placed on first end  31  of post  30 . Retaining band  52  may be placed on the exterior of post  30  to provide additional strength. Retaining band  52  may be formed from various types of metals and/or composite materials. For some applications retaining band  52  may be formed from a relatively strong steel alloy to provide additional support to allow post  30  to handle side impact forces on edges  41  and  42  from cables  60   a,    60   b  and  60   c  during a vehicle impact. 
         [0053]    During installation of cable safety system  20 , cable  60   c  may be disposed within slot  40  resting on bottom  43  thereof. Since post  30  has a generally closed cross section defined in part by the bent edges of legs  35  and  36 , a relatively simple first spacer block  46  may be inserted or dropped into post  30  to rest upon cable  60   c.  Block  46  may have a generally rectangular configuration with a thickness satisfactory for insertion within the cross section of post  30 . For some applications spacer block  46  may be formed from recycled material. The height of spacer block  46  is selected to correspond with the desired vertical spacing between cable  60   c  and  60   b.    
         [0054]    Cable  60   b  may then be inserted into slot  40  after spacer block  46  has been disposed on cable  60   c.  Second spacer block  48  may then be installed within post  40  with one end resting on cable  60   b  opposite from spacer block  46 . The height of second spacer block  48  is preferably selected to correspond with the desired vertical spacing between cables  60   b  and  60   a.  Spacer block  48  may be formed from recycles material. 
         [0055]    Cable  60   a  may then be installed within slot  30  resting on spacer block  48  opposite from cable  60   b.  One or more retaining bands  52  may be secured with the exterior of post  40  between cables  60   a  and  60   b  and/or cables  60   b  and  60   c.  Cap  50  may then be placed over first end  31  of post  30 . 
         [0056]      FIG. 6  shows a single spacer  146  which may be satisfactorily used to position cable  60   a,    60   b  and  60   c  at a desired vertical spacings relative to each other within slot  40 . For the embodiment of the present disclosure as shown in  FIG. 6 , spacer  146  has a generally I-shaped configuration. Recesses  160   a  and  160   c  may be formed in opposite ends of spacer  146 . Another recess  160   b  may be formed in one edge of spacer  146  intermediate the ends thereof. The dimensions of recess  160   a,    160   b  and  160   c  are selected to accommodate cable  60   a,    60   b  and  60   c.  The distance between recess  160   a,    160   b  and  160   c  are selected to correspond with the desired vertical spacing between corresponding cable  60   a,    60   b  and  60   c.    
         [0057]    Spacer  146  may be formed from a wide variety of materials including polymeric materials, elastomeric materials, recycled materials, structural foam materials, composite materials, wood and/or lightweight metal alloys. For some applications spacer  146  may be formed from recycled rubber and/or other recycled plastic materials. The present invention is not limited to forming spacer  146  from any specific type of material or with any specific dimensions or configurations. 
         [0058]    Typical installation procedures for a cable safety system incorporating teachings of the present invention includes installing posts  30  along with anchors  24  and  26  or anchor  24   a  and  26   a  at desired locations adjacent to a roadway and/or median (not expressly shown). Cables  60   a - 60   d  may be rolled out and placed on the ground extending generally longitudinally between anchors  24  and  26  or anchors  24   a  and  26   a.  Spacers  146 , retaining bands  52  and end caps  50  may also be placed adjacent to each post  30  as desired for the specific installation. Cables  60   a - 60   d  may include prefabricated fittings satisfactory for engagement with anchors  24  and  26  or anchors  24   a  and  26   a.  Alternatively, appropriate fittings (not expressly shown) may be attached with each end of respective cables  60   a - 60   d.    
         [0059]    One end of each cables  60   a - 60   d  may be connected with a respective first anchor. Appropriate tension may then be applied to each cable  60   a - 60   d  corresponding to a value of approximately 95% of the desired tension depending upon anticipated ambient temperature and other environmental conditions. Each cable  60   a - 60   d  may then be marked, cut and an appropriate fitting attached. The other end or the second end of each cable may then be coupled with a respective second anchor. Conventional procedures may be used to adjust the tension in cables  60   a - 60   d  to the desired values. Appropriate spacers  146  may then be inserted within each post  30 . Retaining bands  52  and end caps  50  may then be attached to each post. 
         [0060]    For some applications, cable  60   a,    60   b  and  60   c  may be attached with anchor  24  and extended horizontally through each slot  40  formed in the associated support post  30 . A respective spacer may then be inserted into each support post  30  to provide desired vertical spacing between cables  60   a,    60   b  and  60   c.    FIG. 7  is a schematic drawing which shows one example of installing spacer  146  within post  30  after cables  60   a,    60   b  and  60   c  have been placed within slot  40 . 
         [0061]      FIG. 8   a  is a schematic drawing which shows the results of a vehicle impact with cables  60   a,    60   b  and  60   c  adjacent to post  30 . The force of the impacting vehicle will tend to bend post  30  from a generally vertical position towards a horizontal position. As previously noted, cables  60   a,    60   b  and  60   c  will tend to slide from or be released from associated slot  40  as the angle of bending of post  30  from a vertical position increases. One aspect of the present disclosure includes forming one or more restrictions within each slot to help retain associated cables within the slot when a vehicle impacts the associated safety barrier. For example, support post  30   a  is shown in  FIG. 8   b  with cable  60   a,    60   b  and  60   c  retained within slot  40   a  by restrictions formed along edges  41   a  and  42   a.  As a result of the restrictions formed within slot  40   a,  cables  60   a,    60   b  and  60   c  will be retained within slot  40   a  when post  30   a  is bent at the same angle from vertical as post  30 . See  FIG. 8   b.    
         [0062]      FIG. 9  is an enlarged schematic drawing showing post  30   a  having slot  40   a  form thereon with a plurality of restrictions and/or projections formed in each edge  41   a  and  42   a.  For the embodiment of the present disclosure as shown in  FIG. 9  the location and configurations of the restrictions formed in edges  41   a  and  42   a  are selected to correspond generally with the desired location for associated cables  60   a,    60   b  and  60   c.    
         [0063]      FIGS. 10   a - 10   i  are schematic drawings showing various cross sections for support posts incorporating teachings of the present disclosure. Post  130   a,    130   c,    130   d,    130   f,    130   g  and  130   h  do not have any sharp edges exposed to vehicle traffic traveling along an adjacent roadway. Slots  40  may be formed in each post  130   a - 130   h  to receive respective cables therein. 
         [0064]      FIG. 11  is a schematic drawing of a particular embodiment of cable safety system  20  utilizing four cables  60  to improve the prevention of motor vehicles from leaving the roadway and the redirection of vehicles away from hazardous areas without causing serious injuries to the vehicle&#39;s occupants or other motorists. In particular, cables  60   a,    60   b,    60   c,  and  60   d  of cable safety system  20  may prevent or reduce the likelihood of a low profile vehicle passing under cable safety system  20  in the event of an impact, while also minimizing the risk of higher-profile vehicles from passing over or through cable safety system  20 . The use of four cables  60  provides numerous advantages, including enabling a shorter and thinner support post  30  design, as well as enabling the cost-effective capture of more and varied types of vehicles upon impact with cable safety system  20 . 
         [0065]      FIGS. 12A and 12B  are schematic drawing showing a particular embodiment of support post  30   b  utilized in certain embodiments of cable safety system  20 .  FIG. 12  shows support post  30   b  that accommodates four cables  60  (cables  60   a,    60   b,    60   c,  and  60   d ). Cables  60   a  and  60   b  are positioned in slot  40   b.  As previously noted, cables  60   a  and  60   b  will tend to slide from or be released from associated slot  40  as the angle of bending of post  30  from a vertical position increases. One aspect of the present disclosure includes forming one or more restrictions within each slot to help retain associated cables within the slot when a vehicle impacts the associated safety barrier. For example, support post  30   b  is shown in  FIG. 12A and 12B  with cable  60   a  and  60   b  retained within slot  40   b  by restrictions formed along edges  41   b  and  42   b.  As a result of the restrictions formed within slot  40   b,  cables  60   a  and  60   b  will be retained within slot  40   b  when support post  30   b  is bent at the same angle from vertical as support post  30   b.    
         [0066]      FIGS. 12A and 12B  also show a particular embodiment of support post  30   b  in which cables  60   c  and  60   d  are positioned on the outside of support post  30   b  using fastener  38 . Fastener  38  may represent an eye bolt, hook bolt, or other suitable retainer for cable  60 . In an installed configuration, cable  60   c  may be positioned on the side of support post  30   b  closest to the roadway. Cable  60   d  may be positioned on the opposite of support post  30   b  on which cable  60   c  is installed. That is, cable  60   d  may be positioned on a side of support post  30   b  closest to a median between roadways. For example, cable safety system  20  may be installed on or near a median between a southbound roadway and a northbound roadway. Cable  60   c  is advantageously positioned on support post  30   b  to prevent or reduce the likelihood of a northbound vehicle on the northbound roadway from crossing into the median upon impact with cable safety system  20 , and heading into southbound traffic on the southbound roadway. Cable  60   d  is advantageously positioned on support post  30   b  to prevent or reduce the likelihood of a southbound vehicle on the southbound roadway from submarining, or passing under, cable safety system  20  and heading into northbound traffic. 
         [0067]    Cables  60   a,    60   b,    60   c,  and  60   d  may be advantageously positioned along relative heights of support post  30   b  to minimize the risk of vehicles passing over, under, or through cable safety system  20 . In particular, from the lowest cable to the highest cable, cable  60   d  may be positioned approximately one foot, six inches (1′-6″) from ground level. Cable  60   c  may be positioned approximately two feet, six inches (2′-6″) from ground level. Cable  60   b  may be positioned approximately three feet, two inches (3′-2″) from ground level. Cable  60   a  may be positioned approximately three feet, six inches (3′-6″) from ground level. Advantageously placing cables  60  along these relative vertical positions of support post  30   b  may prevent or reduce the likelihood of lower-profile vehicles, such as subcompact cars, from submarining, or passing under, cable safety system  20 . Further, higher-profile vehicles, such as pickup-trucks and vans, may be prevented from passing over, or through cable safety system  10 . 
         [0068]      FIGS. 13A and 13B  show schematic views of slots  40   a  and  40   b  positioned in support posts  30   a  and  30   b,  respectively.  FIG. 13   a  shows slot  40   a  suitable for use in a three-cable cable safety system  20 . Slot  40   a  accommodates cables  60   a,    60   b  and  60   c.  In particular embodiments, slot  40   a  may be open at a top end, positioned at the top of post  30   a,  and may have an overall length of eleven and thirteen sixteenths inches (11 13/16″). Slot  40   a  may be one and three-eighths inches (1⅜″) wide at its widest extent, and may include three restrictions formed along edges  41   a  and  42   a  that are each thirteen sixteenths inches ( 13/16″) wide. As shown in  FIG. 13A , cables  60   a,    60   b,  and  60   c  are each positioned in one of the areas of widest extent between the restrictions. The vertical distance between each restriction may be four and five sixteenths inches (4 5/16″). An opening of slot  40   a  may be fifteen sixteenths inches ( 15/16″). In this configuration, support post  30   a  may be four inches (4″) wide, with a distance from the center of slot  40   a  to an edge of post  30   a  of two inches (2″). 
         [0069]      FIG. 13B  shows a slot  40   b  suitable for use in a four-cable cable safety system  20 . Slot  40   b  accommodates cables  60   a  and  60   b.  Two additional cables (such as, for example, cables  60   c  and  60   d ) may be positioned on the outside of support post  30   b,  as discussed above. In particular embodiments, slot  40   b  may be open at a top end, positioned at the top of support post  30   b,  and may have an overall length of eight and one-half inches (8½″). Slot  40   b  may be one inch (1″) wide at its widest extent, and may include two restrictions formed along edges  41   b  and  42   b  that are each thirteen sixteenths inches ( 13/16″) wide. Cables  60   a  and  60   b  are each positioned in one of the areas of widest extent between the restrictions. The vertical distance between each restriction may be four and five sixteenths inches (4 5/16″). An opening of slot  40   b  at the top of support post  30   b  may be fifteen sixteenths inches ( 15/16″) wide. In this configuration, support post  30   b  may be three inches (3″) wide, with a distance from the center of slot  40   b  to an edge of support post  30   b  of one and one-half inches (1½″). 
         [0070]    As compared with slot  40   a,  slot  40   b  has narrower width between edges  41   b  and  42   b  in which cables  60  are positioned. This reduced distance between edges  41   b  and  42   b  allows for cables  60  and support post  30   b  to interact more quickly in the manner described above with respect to  FIG. 8 . Because cables  60  and support post  30   b  are able to start working more quickly in slot  40   b  (as compared to cables  60  in slot  40   a  and post  30   a ), vehicles may be more effectively redirected away from away from hazardous areas by enabling cables  60  to provide resistance to vehicles impacting cable safety system  20  sooner after impact. 
         [0071]    Moreover, because of the smaller overall dimensions of support post  30   b,  support post  30   b  may be manufactured at a reduced cost compared with previous designs. In particular, the inclusion of four cables  60  in cable safety system  20  allows for a shorter overall height of support post  30   b.  A fourth cable  60  enables the top-most cable  60  to be positioned higher relative to ground level than previous systems. A higher overall cable height enables support post  30   b  to be shorter overall. Additionally, the inclusion of four cables  60  may allow for the use of a thinner web in support post  30   b.  Additionally, cable safety system  20  may be manufactured without punching holes in the bottom of support post  30 , which may substantially reduces the manufacturing cost of support post  30   b.    
         [0072]    In combination with four cables  60  and other aspects of cable safety system  20 , the smaller and thinner size of support post  30   b  is effective to improve redirection of vehicles away from hazardous areas without causing serious injuries to the vehicle&#39;s occupants or other motorists. A smaller post in combination with a three-cable design would not have performed as effectively because cable safety system  20  would have been less effective at preventing vehicles from submarining or passing through cable safety system  20  as compared to a four-cable design. A combination of a smaller and thinner support post  30   b  may enable support post  30   b  to be manufactured at a weight of 5.7 pounds per foot, compared with a weight of 7.7 pounds per foot for previous designs, thereby enabling substantial cost savings during manufacture and maintenance. 
         [0073]    A typical installation process in accordance with particular embodiments of the present disclosure is now described. Posts  30  and anchors  24  and  26  are installed at desired location adjacent to a roadway and/or median. Cables are rolled out and spacers are placed, retaining the band and cap at each post. Cables are connected with appropriate fittings if the cables do not include prefabricated fittings. One end of each cable is connected with anchor  26 . Each cable is tensioned to a value of approximately 95% of the desired tension depending upon temperature and other environmental conditions. Each cable is marked, and an appropriate fitting is cut and attached. Each end of the respective cables is connected with the second anchor  26 . The tension in the is adjusted cables to a desired level. Spacers are installed within each post. A retaining band and cap is attached at each post. 
         [0074]    Although embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alternations can be made herein without departing from the spirit and scope of the invention as defined by the following claims.