You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of and is a continuation-in-part of U.S. patent application Ser. No. 14/052,017 filed Oct. 11, 2013. The above-referenced application is hereby incorporated by reference herein in its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a barrier system particularly but not exclusively a road safety barrier system. 
     BACKGROUND OF THE INVENTION 
     Road safety barriers are designed to shield motorists from impacts with roadside hazards such as trees, utility poles, steep embankments, culverts and other vehicles. Road safety barriers are typically classified into three categories: rigid barriers; flexible barriers; and semi-rigid barriers. 
     Rigid barriers are generally employed where there is minimal margin for vehicles to move outside allocated traffic lanes. Such barriers may, for example, be formed of solid concrete. A disadvantage of concrete barriers is that vehicles that collide with the barriers could face severe impact damage. 
     Flexible barriers are employed where there is significant space beside the roadway to accommodate movement of a vehicle outside the traffic lanes. One such flexible barrier is formed of a series of tensioned cables. 
     Where there is lesser degree of available space adjacent a roadway, a semi-flexible barrier will generally be employed. One such barrier includes a series of upright posts along the roadside that support a guardrail. The guardrail serves as a containment ribbon under impact to absorb and re-direct a vehicle. During impact, the support posts may be knocked down and the guardrail needs to be maintained at a suitable height, to provide the required containment function, instead of being dragged down and under the vehicle as a result of continued attachment to the posts. 
     A number of mechanisms have been used in an attempt to maintain the height of the guardrail during impact. A first mechanism is to introduce a spacer block between the supporting posts and the guardrail. The spacer block rotates over the post as the post is knocked down to keep the guardrail elevated, until the guardrail physically disengages from the post. The spacer block minimized snagging of the vehicle on the post, due to the spacing between the guardrail and the posts, and reduces the potential for the vehicle to vault over the guardrail as the post height is maintained during the initial stages of impact. However, a problem with the spacer block arrangement is that the posts and spacer blocks are generally formed of open steel C-sections to minimize costs and both the posts and blocks tend to plastically crush and deform on impact instead of deflecting in order to separate from the guardrail. This ultimately has the effect of dragging the guardrail under the vehicle as a result of the vehicle fully impacting with the barrier. 
     Another mechanism to facilitate separation of the guardrail from the posts is to fix connecting collars to the guardrail. The collars are designed as sliding carriages that are arranged to slide over the posts and locate the guardrail at an appropriate height. When a vehicle impacts the barrier, the posts collapse and the collars freely slide off the ends of the posts. Once the collars are released, the guardrail becomes a substantially flexible ribbon that then demands a considerable distance be provided adjacent the roadway to arrest and redirect a vehicle. 
     Another mechanism is to attach the guardrail directly to the supporting posts by countersunk bolts that have a specific tapered head designed to pull through the guardrail under load. However, this mechanism has not been widely implemented since cheaper, non-tapered fasteners are readily available substitution may occur. If cheaper fasteners are installed, the guardrail will likely not function appropriately in the event of an impact. For safety reasons, this mechanism is not widely endorsed. 
     Any reference to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the date of this application. 
     OBJECT OF THE INVENTION 
     The present invention seeks to provide an improved or alternative barrier system. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a vehicle containment barrier system, comprising: a plurality of supports that each have a top end and a bottom end, wherein the supports are generally vertically orientated, and each include: a front side and rear side; a tab formed in the front side that is defined by reduced thickness area in the support comprising a recessed channel around the outer periphery of the tab, and a connection portion, wherein the connection portion is located at a bottom region of the tab and the reduced thickness areas is positioned at sides and a top region of the tab; a guardrail that is coupled to the supports so as to extend laterally across the front sides of the supports; and a plurality of connectors that couple the guardrail to the supports at the tabs, wherein the connectors are located within the outer periphery of the tabs; and wherein when a vehicle strikes the guardrail at the front side of the supports, the sides and top region of the tab move outwardly away from the support while the bottom region of the tab remains connected to the support and the tab remains connected to the guardrail, thereby suspending the guardrail above the ground while the supports move away from their generally vertical orientation as the vehicle impacts the barrier system. 
     In another aspect, there is provided a barrier system including a guardrail, a support to hold the guardrail in position and a fastener to attach the guardrail to the support, wherein the support has a weakened zone to facilitate the fastener releasing from the support when the support is subject to impact forces: wherein the weakened zone is arranged about a connection region of the support, though which the fastener is attached; and wherein the connection region is designed to remain attached to the fastener and guardrail and the support is adapted to separate along the weakened zone, under initial deflection of the support away from the guardrail, such that a tab of support material remains attached to the guardrail. 
     In another aspect, there is provided a barrier system with a guardrail for containing a vehicle impact including upright supports to suspend the guardrail above a ground surface and associated fasteners for connecting the guardrail to the supports, wherein the supports each include a weakened zone around a connection region where the fasteners are coupled to the respective supports, the weakened zone allowing the fasteners to release from the supports while remaining attached to the guardrail, when the supports move away from an upright orientation toward the ground surface when a vehicle impacts the barrier system. 
     Preferably, the weakened zone is arranged about a connection region of the support, though which the fastener is attached. 
     In another aspect, there is provided a support for use in the above system, the support having a weakened zone arranged about a connection region of the support, through which a fastener is attached to secure a guardrail to the support, the weakened zone facilitating release of the fastener from the support when the support is deflected away from the guardrail. 
     Preferably, the weakened zone is configured such that the tab is formed as an elongate vertical strip, and the separation propagates from an upper section of the support, toward a lower section of the support, as the support deflects away from the guardrail. 
     Preferably, the tab is designed to separate from the remainder of the support, upon further deflection of the support away from the guardrail. 
     Preferably, the weakened zone is in the form of a reduced thickness section of the support. 
     Preferably, the section includes a slot or perforation. More preferably, the section includes an array of slots or perforations. 
     Preferably, the weakened zone is square, rectangular, circular, C or U shaped. 
     Preferably, the weakened zone is continuously or intermittently spaced around the connection region. 
     Preferably, the support is in the form of a blocking piece attached to a post. 
     Alternatively, the support is in the form of a post. Preferably, the post has a square hollow section, rectangular hollow section, round hollow section, C section, U section, Z section, I post, H post or open hat cross section. 
     Preferably, the guardrail has a W-shaped cross section and a single fastener is used to connect the guardrail to the support. Alternatively, the guardrail has a triple crest section with a double trough, adapted to receive the fastener through one of the troughs. Preferably, a second fastener is fixed to the support through the second trough. 
     Preferably, the system includes a plurality of supports, with associated weakened zones, for attaching the guardrail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is more fully described, with reference to the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a barrier system; 
         FIG. 2  is a plan view of a guardrail attached to a support; 
         FIG. 3  is a perspective view of the support of  FIG. 2 ; 
         FIG. 4  is a front view of an alternative support with slots in a cross array; 
         FIG. 5  is a front view of a different support with slots in a square array; 
         FIG. 6  is a front view of another example of a support with an inverted U-shaped slot; 
         FIG. 7  is a front view of a further example of a support with a U-shaped slot; 
         FIG. 8  is a front view of another support with an I-shaped slot; 
         FIG. 9  is a front view of yet another example of a support with a D-shaped slot; 
         FIG. 10  is a front view of a support with a tab; 
         FIG. 11  is a front view of another support with a tab; 
         FIG. 12  is a front view of an alternative support with a forked tab; 
         FIG. 13  is a front view of a further support with an inverted forked tab; 
         FIG. 14  is a front view of yet another support with an oval-shaped perforation; 
         FIG. 15  is a front view of still another support with a square-shaped perforation; 
         FIG. 16  is a side view of the guardrail fixed to a support; 
         FIG. 17  is a side view of an alternative guardrail fixed to the support; 
         FIG. 18  is a side view of the guardrail of  FIG. 17  attached to the post with two fasteners; 
         FIG. 19  is a side view of the post of  FIG. 16  secured in the ground; 
         FIG. 20  is a side view of the post of  FIG. 19  under partial deflection; 
         FIG. 21  is a side view of the post of  FIG. 20  after further deflection; 
         FIG. 22  is a front view of a different post showing another tab construction; 
         FIG. 23  is a side view of a guardrail fixed to a support; 
         FIG. 24  is a side view of the support of  FIG. 23  under partial deflection; 
         FIG. 25  is a side view of the support of  FIG. 24  after further deflection; and 
         FIG. 26  is a partial perspective view of anther support. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Throughout the following description, like reference numerals will be used to denote like parts. 
     Referring firstly to  FIG. 1 , a barrier system  1  is shown as including a series of supports  2  in the form of posts  3  fixed in a ground surface  4 . Alternatively, each post could be mounted to a base plate that is bolted to a footing. Each post  3  has a front side  5 , onto which is mounted a guardrail  6 . 
     The guardrail  6  is formed as an elongate W-section. Adjacent guardrails  7  can be connected to the guardrail  6  by bolts  8  that pass through aligned openings  9  and are secured in place with nuts  10 , so that the guardrails  6 ,  7  form a structurally continuous rail. 
     In order to mount the rail  6  to one of the posts  3 , a connector or fastener  11  is provided though a hole  12  in the guardrail  6  and is fixed in a corresponding aperture  13  in the post  3  with a nut  14  that locks the fastener  11  in place. The hole  12  in the guardrail  6  has a horizontal dimension that accommodates some misalignment between the guardrail  6  and the aperture  13  in the post  3 . Likewise, the aperture  13  has a vertical dimension that allows for a degree of vertical misalignment. 
     The aperture  13  is provided in a connection region  15  of the post  3  and a weakened zone  16 , is arranged about the connection region  15 . In this case, the weakened zone  16  is in the form of a vertical slot  17  arranged to either side of the aperture  13 . 
     The function of the weakened zone  16  is to cause the post  3  to structurally fail or shear around the aperture  13 , as the post  3  is deflected away from the guardrail  6 , such as during a vehicle impact. The structural failure allows the fastener  11  and nut  14  to pull free from the post  3 . This then allows the guardrail  6  to remain at a suitable height to function as a containment ribbon to absorb impact forces and redirect the vehicle. As such, a shear strength of the connection region  15  is designed, by way of the weakened zone  16 , to be less than a connection force between the fastener  11  and the guardrail  6 . 
     Referring now to  FIG. 2 , a plan view is shown, which illustrates the connection between the post  3  and guardrail  6 . The fastener  11  is more clearly shown as a mushroom head bolt  18  that is secured through the front face  5  of the post  3  and is fixed in place with the nut  14 . The post  3  has a closed rectangular cross-section which is particularly strong and light weight, although other suitable forms of cross-section could instead be used, as required. For example, the cross-section could be formed with a square hollow section, round hollow section, C section, U section, Z section, I post, H post or open hat section. 
     Referring now to  FIG. 3 , the weakened zone  16  is in the form of a reduced thickness section of the post  3  and, more particularly, an inverted U-shaped slot  19 . For the purpose of  FIG. 3  and all subsequent Figures, where there are like parts shown in the drawings, like reference numerals will be used describe those like parts. 
     The slot  19  defines a tab  20  that includes the connection region  15  with the aperture  13 . When the post is initially deflected, the connection region  13  remains attached to the fastener  11  and the guardrail  6  while the tab separates from the remainder of the post  6  along the weakened zone. 
     More particularly, the tab  20  is in the form of a vertical strip  21  that is adapted to lift clear of the front face  5 . The separation between the tab  20  and the post  3  propagates from an upper section  22  of the post  3 , toward a lower section  23 , as the post  3  deflects downward. 
     The tab  20  is designed to shear away from the post  3 , upon further deflection of the post  3 . 
       FIGS. 4 and 5  show alternative examples of weakened zones  16 , that are intended to facilitate release of the fastener  11  from the aperture  13 , as opposed to the creation of a tab. In  FIG. 4 , the weakened zone  16  is in the form of slots  24  arranged in a cross configuration. In  FIG. 5 , the slots  25  are arranged in a square array around the connection region  15 . 
       FIGS. 6 and 7  illustrate further examples of the weakened zone  16  being in the form of a U-shape slot  26 , with  FIG. 6  showing an inverted U-shape. In both cases, the weakened zone  16  will result in the connection region  15  being in the form of a tab  20  that is attached to a main body  46  of the support  2  by way of a connection portion  47 . In this case, a separation force shear strength of the connection portion  47  is configured to be less than a connection force between the fastener and guardrail (not shown) so that the tab deflects away from the body  46  under load and then separates from the support  2  as the support moves away from a vertical orientation and then collapses toward a ground surface. 
       FIGS. 8 and 9  show the aperture  13  as a rectangular slot  27  and the weakened zone  16  is then formed by horizontal slots  28  in communication with the aperture  13  whereby the overall zone  16  has an I-shape or D-shape, respectively. 
       FIGS. 10 and 11  illustrate further examples of the weakened zone  16  being in the form of a continuous slot  29  around the connection region  15  and aperture  13  so as to define an associated tab  20 . 
     Turning now to  FIGS. 12 and 13 , the weakened zone  16  is formed by U-shaped slots  30  that interconnect with the aperture  13  so as to define a fork-shaped tab  31 . 
     In  FIGS. 14 and 15 , the slots  32  are formed intermittently and may in part be in the form of perforations  33 .  FIG. 14  illustrates the perforations  33  in an oval array while  FIG. 15  shows a square array formed of a combination of slots  32  and perforations  33 . 
     It should be appreciated that all of the slots or perforations described above embody a weakened zone  16  on the post  3 . The perforations and slots can, of course be in any suitable array and need not in fact penetrate the thickness of the post. For example, the weakened zone  16  may be provided in the form of a reduced thickness zone of the post, as opposed to an actual slot or perforation. 
     Referring now to  FIG. 16 , a side view of the post  3  and guardrail  6  is shown. As described with reference to  FIG. 1 , the guardrail has a W-shaped cross section and only a single fastener  11  is used in trough  34  to secure the guardrail  6  to the post  3 . 
     The guardrail  6  could, however, be of any suitable configuration and more than one fastener might be used.  FIG. 17  illustrates a guardrail  6  with a triple-crest and a double trough, for increased stiffness, that can still be fastened to the post with a single fastener  11 .  FIG. 18  illustrates the guardrail attached to the post with a second fastener  35 . 
     Turning now to  FIGS. 19 to 21 , the operation of the barrier system  1  is described in more detail. 
       FIG. 19  shows the guardrail  6  fixed to a post  3  with a fastener  11 , before impact of a vehicle.  FIG. 20  shows initial deflection of the post  3  after impact of the vehicle. As can be seen, the post  3  is deflected downwardly while a tab  20  is separating from the post together with the connector or fastener  11 . 
       FIG. 21  illustrates a condition in which the post  3  has deflected further under impact forces from the vehicle and that has resulted in the tab  20  tearing away from the main body  46  of the post  3 , at the connection portion  47 , so that the guardrail is able to remain elevated, in a suitable position to function as a containment ribbon to absorb and redirect the vehicle impact. 
       FIG. 22  shows a post  3  with a tab  20  that is considerably more elongate than that illustrated in  FIGS. 19 to 21  but which otherwise functions in an identical manner. 
       FIGS. 23 to 25  illustrate the elongate tab  20  in operation during a vehicle impact. The tab  20  also serves to separate from the post  3  when the post is fully deflected, however, the length of the tab  20  results in the guardrail  6  being attached to the post  3  for a longer period prior to separation, which can be advantageous if there is a need to utilize additional impact absorption via the post  3  to contain a vehicle impact, such as where there is limited available space adjacent the barrier system to allow for vehicle redirection. The longer tab also facilitates the rail remaining in a more vertical orientation until separation. 
       FIG. 26  illustrates another support  2  in the form of a sigma post  36 , which is named as a result of the cross-sectional profile resembling the Greek letter E. The post  36  has an open side  37  and a front side  38  with an aperture  39  designed to receive a fastener and nut (not shown). The aperture  39  is formed in a connection region  15  which is defined as a tab  40 , between an arch-like slot  41  and a horizontally extending slot  42  at a base  43  of the tab  40 . A connection portion  47  is located between the slots  41 ,  42 . A small bridge  44  attaches a top end  45  of the tab  40  to a main body  46  of the post  36  to maintain the structural integrity and alignment of the tab  40  with respect to the body  46  such as during transport and installation of the post  36 . The bridge  44  is designed to fail as soon as any significant load is applied to the tab  40 , such as during impact of a vehicle, which will cause the tab  40  to separate from the body  46  as the post  36  moves away from a vertical orientation, toward a ground surface. The bridge  44  can, of course, be omitted if not needed. 
     The guardrail  6  has been described above primarily with reference to attachment to a post  3 . However, it should be appreciated the guardrail  6  can instead be mounted to any support  2 . Indeed, the support  2  could be in the form of a spacer piece that is itself attached to a post  3 . 
     Also, the system  1  has been described specifically with reference to a road barrier system. However, the invention has application to any form of barrier system where containment and redirection of impact is required. 
     Regardless of the application, is it important for the guardrail  6  to disengage from the associated supports  2  in a controlled and relatively predictable manner so that the guardrail remains at a suitable height in order to function as a re-directive ribbon. 
     The system has been described by way of non-limiting example only and many modifications and variations can be made thereto without departing from the spirit and scope of the invention described. 
     LIST OF PARTS 
     
         
           1 . Barrier system 
           2 . Support 
           3 . Post 
           4 . Ground surface 
           5 . Side 
           6 . Guardrail 
           7 . Guardrail 
           8 . Bolts 
           9 . Openings 
           10 . Nuts 
           11 . Fastener 
           12 . Hole 
           13 . Aperture 
           14 . Nut 
           15 . Connection region 
           16 . Weakened zone 
           17 . Vertical slot 
           18 . Bolt 
           19 . Slot 
           20 . Tab 
           21 . Strip 
           22 . Upper section 
           23 . Lower section 
           24 . Slots 
           25 . Slots 
           26 . Slot 
           27 . U-shaped slot 
           28 . Horizontal slots 
           29 . Continuous slot 
           30 . U-shapes slots 
           31 . Fork-shaped tab 
           32 . Slots 
           33 . Perforations 
           34 . Trough 
           35 . Second fastener 
           36 . Post 
           37 . Open side 
           38 . Front side 
           39 . Aperture 
           40 . Tab 
           41 . Slot 
           42 . Slot 
           43 . Base 
           44 . Bridge 
           45 . End 
           46 . Body 
           47 . Connection portion

Summary:
A barrier system including a guardrail, a support to hold the guardrail in position and a fastener to attach the guardrail to the support, wherein the support has a weakened zone to facilitate the fastener releasing from the support when the support is subject to impact forces.