Patent Publication Number: US-2012043516-A1

Title: Crash cushion for roadside object

Description:
The present invention relates to a sacrificial crash cushion for a roadside object, such as a signpost, mast or pylon or the like. The function of the roadside object is not important to the present invention; rather, the present invention is applicable to any roadside object which has sufficient inertia to present a hazard to vulnerable road users (eg motorcyclists, cyclists, and passengers ejected from vehicles during an accident) in collision therewith. 
     A roadside object such as a signpost or lamppost may be a serious hazard to a vehicle&#39;s occupant(s) during an accident, particularly if the vehicle leaves the road and collides (e.g. head-on) with the roadside object. One way of reducing the risk of serious injury to a vehicle&#39;s occupant(s) is to provide crash cushion barriers in front of the roadside object, either to prevent a vehicle from striking the roadside object or reduce the speed with which the vehicle strikes the roadside object. U.S. Pat. No. 4,101,115 discloses a disposable unit which is mounted in front of a concrete abutment, signpost, guard rail or the like to prevent a moving vehicle from annihilation should it strike the abutment, etc. The crash cushion comprises a container, filled with a compressible mixture of cemented vermiculite, which is ground-anchored using cables. Another way of reducing the risk of serious injury to a vehicle&#39;s occupant(s) is to (re)design the roadside objects as sacrificial energy-absorbing structures in their own right so less impact energy is absorbed by the vehicle during a collision. However, it may not always be possible to design the roadside object in such a way. 
     The present applicant has appreciated the need for an improved crash cushion for roadside objects to help protect the most vulnerable road users (eg motorcyclists, cyclists, and passengers ejected from vehicles during an accident) in collision therewith. 
     In accordance with one aspect of the present invention, there is provided a sacrificial crash cushion for a roadside object (e.g. post, mast or pylon), comprising a body defining a chamber containing a sacrificial energy absorber, the chamber having a central region and a lateral region on each side thereof, wherein the lateral regions extend away from the central region such that the body has a profile configured to abut a roadside object, the profile having in each of two spaced-apart locations a contact surface for contacting a roadside object, with the contact surfaces facing in different directions. 
     The resulting sacrificial crash cushion is configured to be fitted to, and at least partially around, the base of a roadside object. This obviates the need for the crash cushion to be anchored direct to the ground. Furthermore, by having a profile which abuts two surfaces of the roadside object which face in different directions, but at least partially towards one another, the sacrificial crash cushion will remain between the roadside object and a person during impact and not be knocked out of the way by the person&#39;s incident momentum. 
     The contact surfaces of the two spaced-apart locations may face in two directions spaced by an angle of between 45° and 135°. In one arrangement, the angle may be about 90°. The body may have a substantially “L”- or “C”-shaped profile or footprint. An “L”-shaped profile or footprint may be suited to roadside objects with a square cross-section (e.g. masts and pylons) and a “C”-shaped profile or footprint may be suited to roadside objects with a circular cross-section (e.g. lampposts). 
     The central region of the chamber may have an arcuate cross-section in a horizontal plane, such that in use the body has at least in part a curved outer peripheral wall (which in use faces away from its roadside object). It is believed the curved outer peripheral wall will exhibit more uniform deformation characteristics to impacts from different directions. Furthermore, the absence of a “sharp” transition from one lateral region to the other may help to avoid localized stress concentrations during an impact which could lead to premature failure of the sacrificial energy absorber. 
     The sacrificial energy absorber may comprise at least one layer of a sheet-form structure which extends from the central region to at least one of the lateral regions of the chamber. The sheet-form structure may even extend from one lateral region of the chamber to the other. The sheet-form structure may comprise a honeycomb structure, possibly a honeycomb structure as described in International application WO98/06553, the entire contents of which are incorporated herein by reference. Alternatively, or additionally, the sacrificial member may comprise a press load (or egg box) structure, possibly as described in International application WO00/31434, the entire contents of which are incorporated herein by reference. The sheet-form structure may define a notional median plane which in use is arranged substantially vertically. The median plane may be curved and may have a footprint following the outline of a front or rear face of the body. 
     The body may comprise at least one opening for receiving a strap to strap the sacrificial crash cushion to a roadside object. For example, one opening may be provided adjacent each lateral region of the chamber. Alternatively, or additionally, the sacrificial crash cushion may further comprise an anchor for securing the body to a roadside object. The anchor may comprise a clamping member, and means for adjusting the position of the clamping member relative to the body. For example, the position adjusting means may comprise a threaded rod part and a corresponding aperture part, configured such that rotation of one part relative to the other adjusts the position of the clamping member relative to the body. With such an arrangement, the sacrificial crash cushion may be clamped in position, against a roadside object with at least a part of the latter between the clamping member and the body. 
     The sacrificial energy absorber may be configured to be “person-friendly”, in other words it may be configured to deform when exposed to a threshold force level which would be generated by an average person hitting the sacrificial energy absorber head-on at a predetermined speed, such as below 30 mph, or even below 20 mph, or possibly even below 10 mph. In this way, the sacrificial energy absorber may start to deform (and hence start to absorb impact energy) before fatal and even serious injuries are inflicted on a vulnerable road user colliding with therewith. Such functionality may be achieved despite the fact that the body and/or sacrificial energy absorber may be non-resilient (eg having a rigid plastic construction). 
     In accordance with another aspect of the present invention, there is provided a method of protecting a vulnerable road user in collision with a roadside object, comprising: providing a sacrificial crash cushion in accordance with the first aspect of the present invention (or embodiments thereof); and securing the sacrificial crash cushion to the roadside object. 
     In accordance with yet another aspect of the present invention, there is provided a highway safety assembly, comprising a roadside object and a sacrificial crash cushion in accordance with the first aspect of the present invention (or embodiments thereof), the sacrificial crash cushion being secured to the roadside object to face in the general direction of oncoming traffic travelling along the road adjacent thereto. 
    
    
     
       An embodiment of the invention will now be described by way of example, and with reference to the accompanying figures in which: 
         FIG. 1  is a perspective view of a sacrificial crash cushion embodying the invention; 
         FIG. 2  is a cut-away perspective view of the sacrificial crash cushion of  FIG. 1  showing a sacrificial energy absorber housed therein; 
         FIG. 3  is a perspective view of the sacrificial energy absorber of  FIG. 2 ; and 
         FIG. 4  is a schematic sectional view of part of the sacrificial crash cushion of  FIG. 1 , showing anchor detail. 
     
    
    
       FIGS. 1 and 2  illustrate a sacrificial crash cushion  10  embodying the present invention. The sacrificial crash cushion  10  has an injection moulded body  12  defining a chamber  14  housing a sacrificial energy absorber  16  (shown fully in  FIG. 3 ). The chamber  14  has a central region  20  and two lateral regions  22 ,  24 , one on each side of the central region  20 . The lateral regions  22 ,  24  extend away from the central region  20  such that the body  12  has a profile  30  configured to abut a roadside object  40  (shown in phantom lines). The profile  30  has two spaced-apart contact surfaces  32 ,  34  which face in different directions. The contact surfaces  32 ,  34  are configured to abut adjacent sides of a roadside object in the form of a square section mast. Thus, the surfaces  32 ,  34  are angularly spaced by about 90°. 
     The central region  20  of the chamber  14  has an arcuate cross-section in a horizontal plane (i.e. the central region  20  has a footprint shaped like a truncated quadrant of a circle). In this way, the body  12  has at least in part a curved outer periphery  36  which faces away from the roadside object  40 . The central region  20  includes an arcuate step  38  to avoid a sharp transition from one lateral region to the other adjacent the roadside object  40 . The sacrificial energy absorber  16  comprises layers of a sheet-form structure  50 , some of which extend from one lateral region  22  through the central region  20  to the other lateral region  24 . The sheet-form structure  50  has the egg-box shape which is disclosed in WO00/31434, the entire contents of which are incorporated by reference. At least one of the sheet-form structures  50  has a notional median plane  52  which is aligned vertically and curves through the chamber  16  in sympathy with curvature of a front wall  54  of the body  12 . Adjacent layers of sheet-form structure  50  are separated by stiff sheet material  56  to help avoid localised stress concentrations in the sacrificial energy absorber  16 . 
       FIG. 4  shows an anchor  60  for securing the body  12  to a roadside object  62 . The anchor  60  comprises a clamping member  64  such as a bar or plate and means  66  for adjusting the position of the clamping member  64  relative to the body  12 . The position adjusting means  66  includes a bolt  68  with a threaded shaft  70  which engages a corresponding aperture  72  in the body  12 . Rotation of the bolt  68  relative to the aperture  72  varies the spacing between the clamping member  64  and body  12  enabling at least part of the roadside object  62  to be trapped therebetween. 
     The body  12  may also have integral openings (not shown) for receiving a strap to strap the sacrificial crash cushion  10  to the roadside object  62 .