Patent Publication Number: US-11384494-B2

Title: Safety trailer

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. application Ser. No. 16/421,350, filed May 23, 2019, which is a continuation of U.S. application Ser. No. 15/655,948, filed Aug. 1, 2017, now U.S. Pat. No. 10,301,787, which is a continuation of U.S. application Ser. No. 15/019,124, filed Feb. 9, 2016, now U.S. Pat. No. 9,725,858, which is a continuation of U.S. application Ser. No. 14/324,720, filed Jul. 7, 2014, now U.S. Pat. No. 9,267,250, which is a continuation of U.S. application Ser. No. 14/106,039, filed Dec. 13, 2013, now U.S. Pat. No. 8,777,255, which is a continuation of U.S. application Ser. No. 13/913,868, filed Jun. 10, 2013, now U.S. Pat. No. 8,628,110 which is a continuation of U.S. application Ser. No. 12/713,822, filed Feb. 26, 2010, now U.S. Pat. No. 8,465,047 which claims the benefits of U.S. Provisional Application Ser. No. 61/156,319, filed Feb. 27, 2009, all having the same title, all of which are incorporated herein by this reference. 
    
    
     FIELD 
     The present invention relates generally to the field of trailers and other types of barriers used to shield road construction workers from traffic. More specifically, the present invention discloses a safety and construction trailer having a safety wall. 
     BACKGROUND 
     Various types of barriers have long been used to protect road construction workers from passing vehicles. For example, cones, barrels and flashing lights have been widely used to warn drivers of construction zones, but provide only limited protection to road construction workers in the event a driver fails to take heed. Some construction projects routinely park a truck or other heavy construction equipment in the lane between the construction zone and on-coming traffic. This reduces the risk of worker injury from traffic in that lane, but does little with regard to errant traffic drifting laterally across lanes into the construction zone. In addition, conventional barriers require significant time and effort to transport to the work site, and expose workers to significant risk of accident while deploying the barrier at the work site. Therefore, a need exists for a safety barrier that can be readily transported to and deployed at the work site. In addition, the safety barrier should protect against lateral incursions by traffic from adjacent lanes, as well as traffic in the same lane. 
     SUMMARY 
     These and other needs are addressed by the various embodiments and configurations of the present invention. 
     In one aspect, a system is provided that includes first and second platforms comprising at least one set of wheels and a safety wall positionable between the first and second platforms to define an area protected from a vehicular incursion. The system further includes one or more of the following features: 
     (A1) the safety wall rotates, by first and second arms, to either side of the first and second platforms, wherein the safety wall has a height of at least about 4 feet from bottom edge to top edge; 
     (A2) the safety wall has a height that is substantially the same as a width of at least one of the first and second platforms, wherein the width ranges from about 6 to about 12 feet; 
     (A3) a weight of the safety wall is at least partially offset by a ballast that is movable, along a fixed path, from one side of the first and/or second platform to the other side; 
     (A4) the safety wall rotates upwardly from a substantially horizontal position to a substantially vertical position; 
     (A5) the safety wall rotates downwardly from a substantially horizontal position to a substantially vertical position, wherein an axis of rotation of the safety wall is horizontally offset from a longitudinal axis of the first and second platforms; 
     (A6) the safety wall rotates counter-clockwise from a substantially horizontal position to a substantially vertical position; 
     (A7) the safety wall moves from a first side of the first and second platforms to an opposing second side, wherein a first surface of the safety wall faces outwardly when the safety wall is positioned on the first side and a different second surface of the safety wall faces outwardly when the safety wall is positioned on the second side; 
     (A8) the safety wall is segmented, with each segment being rotatable with respect to an adjoining segment; 
     (A9) the first platform comprises an asphalt roller to engage a road surface when the safety wall is deployed; 
     (A10) the safety wall moves vertically from a first undeployed position to a second deployed position, the vertical movement being directed by a guide mechanism engaging the safety wall and an adjacent one of the first and second platform; 
     (A11) an inclination of the safety wall, relative to vertical, is adjusted about a substantially stationary point on the safety wall; 
     (A12) the safety wall is displaced linearly from a first side of the first and second platforms to a second side of the first and second platforms; 
     (A13) the safety wall comprises first and second segments, the segments being slidably, but not telescopically, engaged with one another; 
     (A14) the safety wall slidably engages at least one of the first and second platforms; 
     (A15) the safety wall comprises first and second segments, the segments having first and second sets of holes, respectively, oriented transversely to an exteriorly facing surface of the safety wall, the holes, when aligned, receive dowels to lock the first and second segments in position relative to one another; and 
     (A16) at least one of the first and second platforms and the safety wall comprise a guide mechanism that directs the safety wall into a desired position. 
     In a further aspect, a method is provided that includes: 
     (a) providing first and second platforms, comprising at least one set of wheels, and a safety wall positionable between the first and second platforms to define an area protected from a vehicular incursion; and 
     (b) performing at least one of the following steps: 
     (B1) rotating the safety wall, by first and second arms, to either side of the first and second platforms, wherein the safety wall has a height of at least about 4 feet from bottom edge to top edge; 
     (B2) positioning the safety wall on a side of the first and second platforms, the safety wall having a height that is substantially the same as a width of at least one of the first and second platforms, wherein the width ranges from about 6 to about 12 feet; 
     (B3) moving a ballast along a fixed path from one side of the first and/or second platform to the other side to at least partially offset a weight of the safety wall; 
     (B4) rotating the safety wall upwardly from a substantially horizontal position to a substantially vertical position; 
     (B5) rotating the safety wall downwardly from a substantially horizontal position to a substantially vertical position, wherein an axis of rotation of the safety wall is horizontally offset from a longitudinal axis of the first and second platforms; 
     (B6) rotating the safety wall counter-clockwise from a substantially horizontal position to a substantially vertical position; 
     (B7) moving the safety wall from a first side of the first and second platforms to an opposing second side, wherein a first surface of the safety wall faces outwardly when the safety wall is positioned on the first side and a different second surface of the safety wall faces outwardly when the safety wall is positioned on the second side; 
     (B8) positioning the safety wall on a side of the first and second platforms, the safety wall being segmented, with each segment being rotatable with respect to an adjoining segment; 
     (B9) when the safety wall is deployed, engaging a road surface with an asphalt roller on the first platform; 
     (B10) moving the safety wall vertically from a first undeployed position to a second deployed position, the vertical movement being directed by a guide mechanism engaging the safety wall and an adjacent one of the first and second platform; 
     (B11) adjusting an inclination of the safety wall, relative to vertical, about a substantially stationary point on the safety wall; 
     (B12) displacing the safety wall linearly from a first side of the first and second platforms to a second side of the first and second platforms; 
     (B13) positioning the safety wall on a side of the first and second platforms, the safety wall comprising first and second segments, the segments being slidably, but not telescopically, engaged with one another; 
     (B14) positioning the safety wall on a side of the first and second platforms, the safety wall slidably engaging at least one of the first and second platforms; 
     (B15) positioning the safety wall on a side of the first and second platforms, the safety wall comprising first and second segments, the segments having first and second sets of holes, respectively, oriented transversely to an exteriorly facing surface of the safety wall, the holes, when aligned, receive dowels to lock the first and second segments in position relative to one another; and 
     (B16) positioning the safety wall on a side of the first and second platforms, at least one of the first and second platforms and the safety wall comprising a guide mechanism to direct the safety wall into a desired position. 
     The present invention can provide a number of advantages depending on the particular configuration. By way of example, the safety trailer can have sufficient mass and energy absorption to resist, without substantial displacement, the kinetic energy from the impact. The safety wall itself can be made of any rigid material, such as steel. Lighter weight materials having high strength are typically disfavored as their reduced weight is less able to withstand, without significant displacement, the force of a vehicular collision. Energy absorption can be provided by shocks and inflated wheels. Preferred trailer configurations are not deployed on jack stands, which can minimize energy absorption by these mechanisms. 
     The safety wall or barrier (and thus the entire trailer) can be of any selected length or extendable to provide a work area protected from vehicular incursions. This can provide maintenance workers with substantial safety benefits while also providing enhanced driver safety. 
     The traffic-incursion side of the safety trailer, including any elongated safety wall, can be substantially planar to avoid hang ups and snags with an impacting vehicle. Hang ups and snags can direct more kinetic impact energy into the wall and/or cause the vehicle to flip over the safety wall. 
     The height of the safety wall can be high enough to inhibit entry of an impacting vehicle into the protected work area by climbing, flipping, and careening over the wall. 
     End platforms integral to the trailer&#39;s design can minimize the need for workers to leave the protected zone and eliminate the need for separate maintenance vehicles by providing onboard hydraulics, compressors, generators and related power, fuel, water, storage and portable restroom facilities. 
     Optional overhead protection can be extended out over the work area for even greater environmental relief (rain or shine). 
     The trailer can carry independent directional and safety lighting at both ends and will work with any standard semi tractor. Directional lighting and impact-absorbing features incorporated at each end of the trailer and in the rear platform can combine with the safety wall and improved lighting to provide increased protection for both work crews and the public, especially with ever-increasing amounts of night-time construction. Optionally, an impact-absorbing caboose can be attached at the end of the trailer opposite the tractor to provide additional safety lighting and impact protection. 
     The trailer can be designed to eliminate the need for separate lighting trucks or trailers, to reduce glare to traffic, to eliminate the need for separate vehicles pulling portable restroom facilities, to provide better a brighter, more controlled work environment and enhanced safety, and to, among other things, better facilitate 24-hour construction along the nation&#39;s roadways. 
     The trailer can be designed to provide road maintenance personnel with improved protection from ongoing, oncoming and passing traffic, to reduce the ability of passing traffic to see inside the work area (to mitigate rubber-necking and secondary incidents), and to provide a fully-contained, mobile, enhanced environment within which the work crews can function day or night, complete with optional power, lighting, ventilation, heating, cooling, and overhead protection including extendable mesh shading for sun protection, or tarp covering for protection from rain, snow or other inclement weather. 
     Platforms can be provided at both ends of the trailer for hydraulics, compressors, generators, batteries, water misters, water sprayers, pumps for liquid removal from the protected work area, fans, tool storage, related fuel, water, storage, and restroom facilities and other amenities. The trailer can be fully rigged with direction and safety lighting, as well as lighting for the work area and platforms. Power outlets can be provided in the interior of the work area for use with construction tools and equipment, with minimal need for separate power trailers or extended cords. Both the front and rear platforms can provide areas for fuel, water and storage. Additional fuel, water and miscellaneous storage space can be provided in an optional extended caboose of like but lengthened design. 
     Other applications include but are not limited to public safety, portable shielding and shelter, communications and public works. Two or more trailers can be used together to provide a fully enclosed inner area, such as may be necessary in multi-lane freeway environments. 
     With significant shifts to night construction and maintenance, the trailer can provide a well-lit, self-contained, and mobile safety enclosure. Cones can still be used to block lanes, and detection systems or personnel can be used to provide notice of an errant driver, but neither offers physical protection or more than split second warning for drivers who may be under the influence of alcohol or intoxicants, or who, for whatever reason, become fixated on the construction/maintenance equipment or lights and veer into or careen along the same. 
     The safety trailer can be readily, easily and conveniently deployable. The tractor can, for instance, be able to engage the hitch of the safety trailer from multiple directions, rather than only from one specific orientation. The safety trailer can have an air ride on the rear platform to permit either side or the entirety of the front and/or rear platforms to be raised or lowered. 
     The safety trailer can have semi-tractor hookups at both ends and a safety wall that is fixed to one side of the trailer. That side, however, can be changed to the right or left side of the road, depending on the end to which the semi-tractor attaches. A caboose can be attached at the end of the trailer opposite the tractor to provide additional lighting and impact protection. 
     These and other advantages will be apparent from the disclosure of the invention(s) contained herein. 
     As used herein, “at least one”, “one or more”, and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together. 
     It is to be noted that the term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably. 
     The preceding is a simplified summary of the invention to provide an understanding of some aspects of the invention. This summary is neither an extensive nor exhaustive overview of the invention and its various embodiments. It is intended neither to identify key or critical elements of the invention nor to delineate the scope of the invention but to present selected concepts of the invention in a simplified form as an introduction to the more detailed description presented below. As will be appreciated, other embodiments of the invention are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are incorporated into and form a part of the specification to illustrate several examples of the present invention(s). These drawings, together with the description, explain the principles of the invention(s). The drawings simply illustrate preferred and alternative examples of how the invention(s) can be made and used and are not to be construed as limiting the invention(s) to only the illustrated and described examples. Further features and advantages will become apparent from the following, more detailed, description of the various embodiments of the invention(s), as illustrated by the drawings referenced below. 
         FIG. 1  is a side view of an undeployed safety trailer according to an embodiment; 
         FIG. 2  is a side view of a deployed safety trailer according to the embodiment of  FIG. 1 ; 
         FIG. 3  is a cross sectional view along a latitudinal axis of a deployed safety trailer (the axis passing between the first and second platforms) according to an embodiment showing first and second wall structures positioned on either side of the safety trailer; 
         FIG. 4  is a cross sectional view along a latitudinal axis of a deployed safety trailer (the axis passing between the first and second platforms) according to an embodiment showing a wall structure positioned on a first side of the safety trailer; 
         FIG. 5  is a cross sectional view along a latitudinal axis of a deployed safety trailer of  FIG. 4  showing the wall structure positioned on an opposing second side of the safety trailer; 
         FIG. 6  is a cross sectional view along a latitudinal axis of a deployed safety trailer (the axis passing between the first and second platforms) according to an embodiment showing stackable first and second wall structures positioned on either side of the safety trailer; 
         FIG. 7  is a cross sectional view along a latitudinal axis of a deployed safety trailer (the axis passing between the first and second platforms) according to an embodiment showing stackable first and second wall structures positioned on either side of the safety trailer; 
         FIG. 8  is a telescopic tube-in-tube wall structure member according to an embodiment; 
         FIG. 9  is a telescopic tube-in-tube wall structure member according to an embodiment; 
         FIG. 10  is a cross sectional view of a deployed safety trailer taken along line  10 - 10  of  FIG. 12  according to an embodiment with the wall structure on a first side of the trailer; 
         FIG. 11  is a cross sectional view of the deployed safety trailer taken along line  10 - 10  of  FIG. 12  according to an embodiment with the wall structure being moved from the first side to a second side of the trailer; 
         FIG. 12  is the wall structure in isolation of the safety trailer; 
         FIG. 13  is an isometric view of the safety trailer; 
         FIG. 14  is a cross sectional view of a deployed safety trailer taken along line  14 - 14  of  FIG. 16  according to an embodiment with the wall structure being moved to an undeployed position; 
         FIG. 15  is a cross sectional view of a deployed safety trailer taken along line  14 - 14  of  FIG. 16  according to an embodiment with the wall structure being moved to a deployed position; 
         FIG. 16  is an isometric view of the safety trailer; 
         FIG. 17  is a cross sectional view of a deployed safety trailer taken along line  17 - 17  of  FIG. 19  according to an embodiment with the wall structure being moved to an undeployed position; 
         FIG. 18  is a cross sectional view of a deployed safety trailer taken along line  17 - 17  of  FIG. 19  according to an embodiment with the wall structure being moved to a deployed position; 
         FIG. 19  is an isometric view of the safety trailer; 
         FIG. 20  is a cross sectional view of a deployed safety trailer taken along line  20 - 20  of  FIG. 22  according to an embodiment with the wall structure being moved to a deployed position; 
         FIG. 21  is a cross sectional view of a deployed safety trailer taken along line  20 - 20  of  FIG. 22  according to an embodiment with the wall structure being moved to an undeployed position; 
         FIG. 22  is an isometric view of the safety trailer; 
         FIG. 23  is a cross sectional view of a deployed safety trailer taken along line  23 - 23  of  FIG. 25  according to an embodiment with the wall structure being moved to a first side of the trailer; 
         FIG. 24  is a cross sectional view of a deployed safety trailer taken along line  23 - 23  of  FIG. 25  according to an embodiment with the wall structure being moved to a second side of the trailer; 
         FIG. 25  is an isometric view of the safety trailer; 
         FIG. 26  is a plan view of a partially deployed safety wall according to an embodiment; 
         FIG. 27  is a plan view of an undeployed safety wall according to the embodiment of  FIG. 26 ; 
         FIG. 28  is an isometric view of the deployed safety wall according to the embodiment of  FIG. 26 ; 
         FIG. 29  is a plan view of an undeployed safety wall according to an embodiment; 
         FIG. 30  is a plan view of a partially deployed safety wall according to the embodiment of  FIG. 29 ; 
         FIG. 31  is an isometric view of the deployed safety wall according to the embodiment of  FIG. 29 ; 
         FIG. 32  is a plan view of an undeployed safety wall with an asphalt roller-equipped second platform according to an embodiment; 
         FIG. 33  is a plan view of an undeployed safety wall with a side dump-equipped second platform according to an embodiment; 
         FIG. 34  is a cross sectional view of a safety trailer, with an undeployed safety wall, taken along line  34 - 34  of  FIG. 36  according to an embodiment; 
         FIG. 35  is a cross sectional view of the safety trailer of  FIG. 34  with a deployed safety wall; 
         FIG. 36  is an isometric view of the safety trailer of  FIG. 34  with a deployed safety wall; 
         FIG. 37  is a cross sectional view of a safety trailer, with a deployed safety wall, taken along line  37 - 37  of  FIG. 39  according to an embodiment; 
         FIG. 38  is a cross sectional view of a safety trailer, with an undeployed safety wall, taken along line  37 - 37  of  FIG. 38 ; 
         FIG. 39  is an isometric view of the safety trailer of  FIG. 37 ; 
         FIG. 40  is a perspective view of the cable mechanism of the safety wall of  FIG. 37 ; 
         FIG. 41  is a side view of a safety wall according to an embodiment; 
         FIG. 42  is a side view of a safety wall according to an embodiment; 
         FIG. 43  is a side view of a safety wall according to an embodiment; 
         FIG. 44  is a side view of a safety wall according to an embodiment; 
         FIG. 45  is a plan view of a safety trailer according to an embodiment; 
         FIG. 46  is an isometric view of the safety trailer of  FIG. 45 ; 
         FIG. 47  is a side view of the safety wall attachment mechanism of  FIG. 45  according to an embodiment; 
         FIG. 48  is a plan view of a safety trailer according to an embodiment; 
         FIG. 49  is an isometric view of the safety trailer of  FIG. 48 ; 
         FIG. 50  is a safety wall deployment mechanism for the safety trailer of  FIG. 48 ; 
         FIG. 51  is a partial isometric view of a safety trailer according to an embodiment; 
         FIG. 52  is a partial isometric view of the safety trailer of  FIG. 51 ; 
         FIG. 53  is an undeployed safety wall according to an embodiment; 
         FIG. 54  is a deployed safety wall according to an embodiment; 
         FIG. 55  is a safety wall according to an embodiment; 
         FIG. 56  is a platform-mounted crane according to an embodiment; 
         FIG. 57  shows a crane-equipped safety trailer according to an embodiment; 
         FIG. 58  shows a deployed safety wall according to an embodiment; 
         FIG. 59  shows a safety trailer according to an embodiment; 
         FIG. 60  shows a deployed safety trailer according to an embodiment; 
         FIG. 61  is a cross section view of a deployed safety trailer taken along line  61 - 61  of  FIG. 63  according to an embodiment; 
         FIG. 62  is a cross sectional view of the deployed safety trailer of  FIG. 61 ; 
         FIG. 63  is an isometric view of the safety trailer of  FIG. 61 ; 
         FIG. 64  is a cross sectional view of an undeployed safety trailer of  FIG. 61 ; 
         FIG. 65  is an isometric view of an undeployed safety trailer according to an embodiment; 
         FIG. 66  is an isometric view of the deployed safety trailer of  FIG. 65 ; 
         FIG. 67  is an isometric view of an undeployed safety trailer according to an embodiment; 
         FIG. 68  is an isometric view of a deployed safety trailer of  FIG. 67 ; 
         FIG. 69  is an isometric view of an undeployed safety trailer according to an embodiment; 
         FIG. 70  is an isometric view of a deployed safety trailer of  FIG. 69 ; 
         FIG. 71  is a cross sectional view of an interface between a safety wall and a platform according to an embodiment; 
         FIG. 72  is a cross sectional view of an interface between a safety wall segment and another safety wall segment according to an embodiment; 
         FIG. 73  is a rear view of a locking mechanism between two expandable and retractable safety wall members according to an embodiment; 
         FIG. 74  is a side view of an interlocking mechanism between a safety wall and adjoining platform according to an embodiment; 
         FIG. 75  is a side view of an interlocking mechanism between adjoining platforms according to an embodiment; 
         FIG. 76  is a side view of an interlocking mechanism between interconnecting safety wall segments according to an embodiment; 
         FIG. 77  is a cross section view taken along line  74 - 74  of  FIG. 76  showing a safety trailer according to another embodiment; 
         FIG. 78  is a cross section view taken along line  74 - 74  of  FIG. 76  showing a safety trailer according to the embodiment; and 
         FIG. 79  is an isometric view of the safety trailer according to the embodiment. 
         FIG. 80  is an isometric view of the safety trailer according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     General 
     In designing a vehicular impact resistant safety trailer, there are a number of design considerations. For example, the safety trailer should have sufficient mass and energy absorption to resist, without substantial displacement, the kinetic energy from the impact. Energy absorption can be provided by shocks and inflated wheels. Deploying the trailer on jack stands can minimize energy absorption by these mechanisms. If there is insufficient mass and energy absorption, the vehicular impact can displace the safety trailer into the protected work area, with concomitant injuries to maintenance personnel. On the oncoming traffic-facing end of the trailer, the safety trailer should have crash attenuation devices to absorb energy from vehicular collisions and lighting and illuminated message boards to provide adequate warnings to drivers. The traffic-incursion side of the safety trailer, including any elongated safety wall, should be substantially planar to avoid hang ups and snags with an impacting vehicle. Hang ups and snags can direct more kinetic impact energy into the wall and/or cause the vehicle to flip over the safety wall. The safety wall, itself, should have sufficient structural strength (e.g., a relatively high tensile and compressive yield strength) and elastic deformation to resist the kinetic energy of vehicular impact. The height of the safety wall should be high enough to inhibit entry of an impacting vehicle into the protected work area by climbing, flipping, and careening over the wall. The safety trailer should have embedded equipment and associated plumbing/wiring to assist workers in the work area. Examples include generators, lighting, compressors, batteries, water misters, water sprayers, pumps for liquid removal from the protected work area, fans, tool storage, and the like. The safety trailer should be readily, easily and conveniently deployable. The tractor should, for instance, be able to engage the hitch of the safety trailer from multiple directions, rather than only from one specific orientation. The safety trailer should have an air ride on the rear platform to permit either side or the entirety of the front and/or rear platforms to be raised or lowered. The various configurations and embodiments disclosed herein have one or more of these features. 
     Rotatable Arm Safety Wall Trailer Designs 
     In a number of safety trailer embodiments, the safety wall rotates to either side of the trailer, by a rotatable arm aligned (in a substantially vertical plane) substantially with the longitudinal axis of the safety trailer. Each of the rotatable arms, when deploying the safety wall, can drop into, or engage, a channel and/or retainer to provide added strength to the safety wall. 
       FIGS. 1-2  depict a safety trailer according to an embodiment of this design. The trailer  100  includes first and second platforms  104  and  108  interconnected by an extendible and retractable safety wall  112 . The safety wall  112  includes first and second sections  120  and  124 , with the first section  120  telescopically receiving the second section  124 .  FIG. 1  depicts the safety wall in an undeployed configuration while  FIG. 2  depicts the safety wall in a deployed configuration. In the undeployed configuration, the safety wall is retracted while in the deployed configuration the safety wall is extended to define a protected work area for maintenance personnel. The first and/or second platforms  104  and  108  each include a ballast  116 , which is positioned on the trailer  100  to offset, at least substantially, the weight of the safety wall  112 . 
       FIGS. 8 and 9  depict how the telescopically engaged first and second sections  120  and  124  of the safety wall  112  are extended and retracted. The safety wall includes a plurality of interconnected structural members, typically in the form of tubes.  FIGS. 8 and 9  depict an exemplary structural member in the safety wall. Both figures depict a tube-in-tube arrangement with very tight clearance (e.g., less than about 5 mm) between the engaged tubes.  FIG. 8  depicts a circular or arcuate structural tube cross section while  FIG. 9  depicts a rectangular tube cross section. 
     With reference to  FIGS. 3-7 , a number of possible safety wall deployed mechanisms are depicted for various trailer embodiments. In all of the mechanisms, the safety wall rotates, via a rotatable arm, about a rotation axis (in a substantially vertical plane containing also the longitudinal axis of the safety trailer) and the safety wall is expandable via a telescopic mechanism similar to that of  FIGS. 1-2 and 8-9 .  FIG. 3  depicts a safety trailer  300  configuration with independently movable (rotatable) first and second safety walls  304  and  306 . Each first and second safety wall  300  and  306  includes a pair of corresponding rotating arms  308 , with a rotating arm of each wall  300  and  306  rotating about a common pivot  320 , the rotational axis  350  of which lies in a vertical plane containing the longitudinal axis of the safety trailer  300 . The ends of the walls  304  and  306  connect to a different pivot. The first and second safety walls  300  and  304  may be positioned one-on-top-of-the-other on a common side of the safety trailer  300  (not shown) to define a partially protected work space having ingress or egress to workers and equipment or on separate sides of the safety trailer  300 , as shown in  FIG. 3 , to define a fully protected and enclosed work space between the walls.  FIGS. 4-5  depict another safety trailer  400  configuration. The safety wall  404  is rotatable, by rotating arms  408  and about front and rear pivots  420 , to either side of the safety trailer  400 . The wall includes upper and lower gussets  412  to provide additional structural support to the exterior panel  416 . 
       FIGS. 6-7  show yet another safety trailer  600  design according to another embodiment. The safety trailer  600  includes first and second telescopically expandable and retractable safety walls  604  and  608  attached, by rotatable arms  610 , to a common pivot  612 , the rotational axis  650  of which typically is substantially parallel to, and may lie in a substantially vertical plane with, a longitudinal axis  700  of the safety trailer  600 . The other ends of the walls  604  and  608  connect to a different common pivot, positioned, relative to pivot  612 , to provide a common axis of rotation.  FIG. 6  shows the first and second safety walls  604  and  608  being positioned, or deployed, on opposing sides of the safety trailer to define a fully enclosed and protected work space between the safety walls.  FIG. 7  shows the first and second safety walls  604  and  608  stacked one-on-top-of-the-other to define a wall that is twice as high as each of the first and second safety walls  604  and  608  and a partially enclosed and protected work space. 
       FIGS. 10-13  depict a safety trailer  1000  configuration according to another embodiment. The safety trailer  1000  includes first and second platforms  1004  and  1008  and an intervening, rotatably positionable, safety wall  1012 . Each of the first and second platforms  1004  and  1008  include ballast  116  that is movably positionable between the opposing first and second sides of the safety trailer  1000  via rails  1016 . Typically, the ballast is positioned on the opposite side of the safety trailer  1000  from the deployed safety wall  1012 . The safety wall  1012  includes first and second “V” shaped rotatable arms  1200 , each rotatable arm  1200  being connected to a different pivot  1050  and having a traffic incursion facing panel  1300 . The respective pivots  1050  of the first and second rotatable arms  1200  typically lie along a common rotation axis, which is generally the longitudinal axis  1100  of the safety trailer  1000 . The width “W.sub.W” of the safety wall  1012  is preferably within about 25% of, more preferably within about 10% of, and even more preferably substantially the same as, the width “W.sub.B” of the bed of the safety trailer  1000 . This width preferably is at least about 4 feet, more preferably at least about 6 feet and even more preferably ranges from about 6 to about 12 feet. 
     Flip Up/Down Safety Wall Trailer Designs 
     In a number of safety trailer embodiments, the safety wall flips up or down when deployed. In these embodiments, the axis of rotation of the safety wall is spatially offset from (to one side of) a longitudinal axis of the safety trailer. Stated another way, a plane containing both the axis of rotation of the safety wall and longitudinal axis of the safety trailer is not vertical but transverse to a vertical plane. In one configuration, the plane containing both axes is substantially horizontal. 
     With reference to  FIGS. 14-16 , a safety trailer  1400  according to an embodiment of this design includes first and second platforms  1404  and  1408  with a safety wall  1412  rotatably engaged with, and positioned between, the platforms. As can be seen from  FIGS. 14-15 , each end of the safety wall engages, via a respective short rotatable arm  1420 , a corresponding pivot  1424 , about which the safety wall  1412  rotates upwards for deployment or downwards for undeployment/transit. An axis of rotation defined by the pivots  1424  is substantially parallel to, but is offset to one side of, a longitudinal axis  1500  of the trailer  1400 . As can be seen in  FIG. 16 , the first and second platforms  1404  and  1408  each include protruding supports  1600  to support the wall when rotated downwards for transit.  FIG. 14  further shows that the upper portion of the deployed wall can be supported/anchored by protruding pins or dowels  1450 . The height of the deployed safety wall is substantially the same as the width of the trailer bed. 
     With reference to  FIGS. 17-19 , a safety trailer  1700  according to an embodiment includes first and second platforms  1704  and  1708  with a safety wall  1712  rotatably engaged with, and positioned between, the platforms. As can be seen from  FIGS. 17-18 , each end of the safety wall engages, via a respective short rotatable arm  1720 , a corresponding pivot  1724 , about which the safety wall  1712  rotates downwards for deployment or upwards for undeployment/transit. As can be seen in  FIG. 19 , the first and second platforms  1704  and  1708  each include a first set of holes  1900  for dowels to support the wall when rotated upwards for transit and a second set of holes  1950  for dowels to support the wall when deployed. The height of the deployed safety wall is substantially the same as the width of the trailer. 
     With reference to  FIGS. 20-22 , a safety trailer  2000  according to an embodiment includes first and second platforms  2004  and  2008  with a safety wall  2012  rotatably engaged with, and positioned between, the platforms. The safety wall  2012  is, in cross-section, rectangularly shaped due to multiple vertical and horizontal tiers of supporting structural members (not shown), such as the structural design of  FIG. 41 or 44 . A planar face  2100  of the safety wall  2012  faces vehicular traffic. The safety wall rotates upwards for undeployment/transit and downwards for deployment. The holes  2200  at each end of the safety wall  2012  are at the interface of the safety wall and adjacent platform and therefore pass through both the end of safety wall and the adjacent face of the platform. The holes, when aligned, receive removable dowels. More specifically, when (in  FIG. 21 ) the safety wall  2012  is undeployed for transit, only the aligned set of holes at the top of the adjacent platform receive a dowel to secure the safety wall for transit. When (in  FIG. 20 ) the safety wall  2012  is deployed, all four sets of aligned holes receive a dowel to secure structurally the safety wall to the adjacent platform against vehicular impact. To rotate the safety wall  2012  upwards or downwards, only the set of holes at the point  2110  of rotation receives a dowel; the other sets of holes do not. As will be appreciated, the number of sets of holes can be more or less and depends on numerous factors, primarily the strength specifications and requirements for the interface. 
     With reference to  FIGS. 74-76 , a safety trailer  7400  according to an embodiment includes first and second platforms  7404  and  7408  with a safety wall  7412  rotatably engaged with, and positioned between, the platforms. The safety wall  2312  is, in cross-section and like safety wall  2012 , rectangularly shaped due to multiple vertical and horizontal tiers of supporting structural members (not shown). The width of the safety wall is substantially the same as the width of the trailer bed and the safety wall is able to rotate, about pivot  7508  (one of which is positioned on each platform), to either side of the safety trailer. In this configuration, the outer skin  7504  of the safety wall faces upwards when not deployed. When the safety wall is deployed to the selected side of the trailer, dowels are placed in the holes  7500  (which align with matching holes in the platform) to impart structural rigidity to the safety wall. 
     With reference to  FIGS. 23-25 , a safety trailer  2300  according to an embodiment includes first and second platforms  2304  and  2308  with a safety wall  2312  rotatably engaged with, and positioned between, the platforms. The safety wall  2312  is, in cross-section and like safety wall  2012 , rectangularly shaped due to multiple vertical and horizontal tiers of supporting structural members (not shown). Discrete or separate planar faces  2400  and  2402  of the safety wall  2312  face vehicular traffic depending on the side of the trailer  2300  on which the wall  2312  is deployed. The safety wall rotates to both sides of the trailer  2300  for deployment, depending on the orientation of the trailer  2300  relative to vehicular traffic. When traffic, for instance, is on the right side (facing forwards) of the trailer  2300 , the safety wall  2312  is deployed in the position shown in  FIGS. 23 and 25 . When traffic is on the left side (facing forwards) of the trailer  2300 , the safety wall is deployed in the position shown in  FIG. 24 . The holes  2500  at each end of the safety wall  2312  are at the interface of the safety wall and adjacent platform and therefore pass through both the end of safety wall and the adjacent face of the platform. The holes, when aligned, receive removable dowels. When the safety wall  2312  is deployed, all four sets of aligned holes receive a dowel to secure structurally the safety wall to the adjacent platform against vehicular impact. To rotate the safety wall  2312  to the left or right, only the set of holes at the point  2410  of rotation receives a dowel; the other sets of holes do not. As will be appreciated, the number of sets of holes can be more or less and depends on numerous factors, primarily the strength specifications and requirements for the interface. 
       FIGS. 34-36  depict yet another safety trailer embodiment. The safety trailer  3400  includes first and second platforms  3404  and  3408  with a safety wall  3500  rotatably positioned therebetween. The safety wall  3500  rotates upwardly for deployment ( FIG. 35 ) and downwardly for undeployment/transit ( FIG. 34 ). The axis of rotation  3600  of the safety wall  3500  is substantially parallel to, but spatially offset from (not in a vertical plane with), a longitudinal axis  3604  of the safety trailer  3400 . To position the safety wall  3500  properly, the wall, before, during, or after rotation, also translates along its length and drops downward (for deployment) or moves upward (for nondeployment/transit). Translation may be effected in any manner known to one of ordinary skill in the art. An example would be to position the hinges  3410 , about which the safety wall  3500  rotates, in a channel (not shown) on the reverse side of the safety wall  3500 . The channel has a specified length to position, at the end of translation, the hinges  3410  and therefore the safety wall  3500  are at a desired height above the road surface  3420 . 
       FIGS. 61-64  depict yet another safety trailer embodiment. The safety trailer  6100  includes first and second platforms  6104  and  6108  with a safety wall  6200  rotatably positioned therebetween. The safety wall  6200  rotates downwardly for deployment ( FIGS. 61-62 ) and upwardly for undeployment/transit ( FIG. 64 ). The axes of rotation  6300  and  6304  of the safety wall  6200  are substantially parallel to, but spatially offset from (not in a vertical plane with), a longitudinal axis  6400  of the safety trailer  6100 . In operation, the safety wall  6200  may be selectively positioned, by selecting an axis of rotation  6300  and  6304 , on either side of the safety trailer  6100 . By way of example, to position the safety wall  6200  on the left side ( FIG. 61 ) of the safety trailer  6100 , the axis of rotation  6300  is disengaged (such as by removing first and second pins or dowels (not shown) from first and second holes  6250   a,b  and/or matching holes in the first and second platforms at first and second interfaces  6350   a,b  between the first and second platforms and the safety wall  6200 . After disengagement, the safety wall  6200  is rotated about rotational axis  6304  into the deployed position on the left side of the safety trailer  6100 . To position the safety wall  6200  on the right side ( FIG. 62 ) of the safety trailer  6100 , the axis of rotation  6304  is disengaged (such as by removing third and fourth pins or dowels (not shown) from first and second holes  6250   c,d  and/or matching holes in the first and second platforms at first and second interfaces  6350   c,d  between the first and second platforms and the safety wall  6200 . After disengagement, the safety wall  6200  is rotated about rotational axis  6300  into the deployed position. To place the safety wall  6200  in the undeployed/transit position, the first, second, third, and fourth sets of holes at the interfaces  6350   a - d  and/or matching holes in the first and second platforms are aligned (by rotating the safety wall as needed) and dowels or pins inserted (if absent) into the aligned set of holes at each interface. When deployed on either side of the trailer, holes  6400  on either end of the wall  6200  align with matching holes in the adjacent platform. Dowels or pins are inserted into the holes to provide structural strength to the interfaces between the platforms and walls. 
     In any of the foregoing embodiments, the safety wall may be lifted or retracted by one or more hydraulic cylinders. Referring to  FIGS. 53-54 , a safety wall  5300  rotatably engages a hydraulic cylinder  5400 , which in turn rotatably engages a platform  5404 . When the safety wall  5300  is not deployed, the hydraulic cylinder  5400  is retracted, as in  FIG. 53 . In one configuration, the safety wall  5300  is substantially horizontal. When the safety wall  5300  is deployed, the hydraulic cylinder  5400  is extended, as in  FIG. 54 . In one configuration, the safety wall  5300  is substantially vertical. This embodiment may be used to make a safety wall deployable on one or both sides of a safety trailer. 
     Accordion-Like Safety Wall Trailer Designs 
     In a number of safety trailer embodiments, the safety wall retracts accordion-like and has multiple axes of rotation that are transverse (typically substantially orthogonal) to a longitudinal axis of the trailer. 
     Referring to  FIGS. 26-28 , a safety trailer  2600  according to an embodiment of this design includes first and second platforms  2604  and  2608  and an accordion-like safety wall  2612  positioned between, and engaged with, the first and second platforms  2604  and  2608 . The safety wall  2612  includes a plurality of rotatably connected wall segments  2704 ,  2708 , and  2712 , each being rotatable, about a vertical axis, with respect to an adjacent wall segment or, as appropriate, an adjacent first or second platform. At each such interface, a hinge-like interconnection is typically employed. When the safety wall  1612  is deployed as in  FIG. 28 , one or more support members  2700  is used to brace the rotatable interconnection between adjacent wall segments or wall segment and adjacent platform to inhibit rotation of the wall segment in the event of vehicular impact. Brackets  2704  are positioned on either side of the rotatable interconnection to receive the support members  2700 . 
     Referring to  FIGS. 29-31 , a safety trailer  2900  according to another embodiment includes first and second platforms  2604  and  2608  and an accordion-like safety wall  2912  positioned between, and engaged with, the first and second platforms  2604  and  2608 . The safety trailer  2900  is similar to the safety trailer  2600  except that it contains more interconnected wall segments  2704 . As will be appreciated, the number of interconnected wall segments  2704  is a function of the desired length of the safety wall (and size of the protected work area). Thus relative to  FIGS. 26-31 , more or fewer wall segments may be employed. 
     Adjustable Inclination Safety Wall Designs 
     In a number of safety trailer embodiments, an orientation/inclination of the safety wall is adjustable to deploy or undeploy the safety wall. 
       FIGS. 37-40  depict a safety trailer according to an embodiment of this design. The safety trailer  3700  includes first and second platforms  3704  and  3708  and first and second safety walls  3712   a,b  positioned between, and engaged with, the first and second platforms  3704  and  3708 . The inclinations of the safety walls  3712   a,b  are vertical when deployed (as in  FIG. 37 ) and nonvertical (or inclined relative to vertical) when undeployed (as in  FIG. 38 ). The inclination is adjusted by one or more arms  3800  (about which the respective wall rotates) and a double spooled cable reel  4000 . The reel  4000  includes first and second cables  4004  and  4008  each spooled around a separate spool. When the reel  4000  is rotated clockwise, cable  4004  is tightened, or collected on the corresponding spool while cable  4008  is loosened, or spooled out on the corresponding spool, and when the reel  400  is rotated counterclockwise, cable  4008  is tightened, or collected on the corresponding spool while cable  4004  is loosened, or spooled out on the corresponding spool. As cable  4004  is collected and cable  4008  spooled out, the safety wall  3712  rotates in the clockwise direction, and as cable  4008  is collected and cable  4004  spooled out, the safety wall  3712  rotates in the counterclockwise direction. In this manner, the safety wall  3712  is rotated into and out of the vertical position. 
     Slide Safety Wall Trailer Designs 
     In a number of safety trailer embodiments, the safety wall is moved from side-to-side by sliding. 
       FIGS. 45-47  depict a safety trailer according to an embodiment of this design. The safety trailer  4500  includes first and second platforms  4504  and  4508  and safety wall  4512  positioned between, and slidingly engaged with, the first and second platforms  4504  and  4508 . The safety wall  4512  is translated linearly back-and-forth between the left and right sides of the safety trailer  4500  depending on the orientation of the safety trailer relative to oncoming traffic. A forklift  4680 , or other suitable equipment, mounted on the safety trailer when in transit, is used to push the safety wall  4512  to the desired position. The linear translation mechanism is depicted in  FIG. 47 . The interface  4700  between the first (and second) platforms  4504  (and  4508 ) includes a channel member  4704  and roller assembly  4708 , which includes a rotatably (relative to the safety wall  4512 ) roller  4710  that rolls from side-to-side in the channel  4712  of the channel member  4704 . When the safety wall  4512  is in the desired position relative to the first and second platforms  4504  and  4508 , one or more dowels  4716  are inserted into aligned pairs of holes, one hole being in the safety wall  4512  and the other being in the adjacent platform, to hold the safety wall  4512  in position in the event of a vehicular impact. 
       FIGS. 48-50  depict a safety trailer according to an embodiment of this design. The safety trailer  4800  includes first and second platforms  4804  and  4808  and safety wall  4812  positioned between, and engaged with, the first and second platforms  4804  and  4808 . As in the case of safety wall  4512 , the safety wall  4812  is translated linearly back-and-forth between the left and right sides of the safety trailer  4800  depending on the orientation of the safety trailer relative to oncoming traffic. Unlike safety wall  4512 , the safety wall  4812  is moved side-to-side by first and second motors  5000   a,b  positioned on either side of the safety wall  4812  (or alternatively positioned inside of the adjacent platform). Each of the motors  5000   a,b  engages a respective gear  5004   a,b  that, in turn, engages a toothed channel  5008  in a channel member  5010  positioned in the adjacent platform. The motors each turn a respective gear to move the safety wall  4812  back-and-forth in the channel  5008 . Because positioning the motors  5000   a,b  on the safety wall  4812  effectively renders the safety wall usable on only one side of the trailer  4800  to resist vehicular impact, it is preferred that the gear  5004   a,b  be rotatably engaged with an adjacent end of the safety wall  4812  and rigidly engaged with a shaft (not shown) of the corresponding motor and the motor be positioned inside of the respective first and second platform  4804  and  4812 . In this manner, each of the opposing sides of the safety wall, when deployed, presents a substantially planar surface to intercept vehicular traffic incursions. 
     Lift Off Safety Wall Trailer Designs 
     In a number of safety trailer embodiments, the safety trailer has an on-board lifting device, such as a crane, to lift a safety wall from a bed of the safety trailer and deploy the safety wall to a selected side of the safety trailer. 
       FIGS. 51-52 and 71  depict a safety trailer according to an embodiment of this design. The safety trailer  5100  includes first and second platforms  5104  and  5108  and safety wall  5112  positioned between, and engaged with, the first and second platforms  5104  and  5108 . The safety trailer  5100  includes a plurality of channels  5200  on each of the first and second platforms  5104  and  5108 , which receive identically shaped tongues  7100  on the reverse side of the safety wall  5112 . When, as in  FIG. 51 , the safety wall is not deployed or in transit mode, the plurality of channels  5200  engage the tongues  7100  in the safety wall  5112 , preventing removal of the safety wall from the bed defined by the first and second platforms. To deploy the safety wall  5112 , the first and second platforms  5104  and  5108  are moved apart, in the direction shown in  FIG. 52 , to disengage the tongues  7100  from the corresponding channels  5200  by moving the tongues linearly out of the channels. In one configuration, independently operable brakes on the second platform are activated to hold the second platform stationary while the first platform is moved in the direction shown. An on board crane  5220 , before or during disengagement of the tongues from the channels, is attached to safety wall, as shown in  FIG. 52 , such that, when the tongues are removed completely from the channels, the safety wall is suspended, by the crane, above the road surface. The safety wall may then be moved to and engaged with, such as by placing dowels in aligned holes at the interface of the safety wall and adjacent platform, the selected side of the safety trailer. To avoid hang ups with an impacting vehicle, the safety wall is deployed with the planar side facing outwardly and the tongues facing inwardly, relative to the work area. 
       FIGS. 56 and 57  depict an embodiment of a safety trailer  5600  in which a crane  5220  is positioned on each of the first and second platforms  5704  and  5708 . One or more sections  5620   a,b  of the safety wall  5612  are removed by the cranes, by attaching the respective booms to different attachment points. The safety wall sections  5620   a,b  are positioned, either end-to-end on one side of and between or one on each side of, the first and second platforms  5604  and  5608 .  FIG. 58  depicts a safety wall  5612  being positioned on one side of the safety trailer  5600 . 
       FIGS. 69 and 70  depict a safety trailer  6900  according to another embodiment. The safety trailer  6900  includes first and second platforms  6904  and  6908  and safety wall  6912  positioned between, and engaged with, the first and second platforms  6904  and  6908 . The safety wall, as in the embodiment of  FIGS. 51-52 and 71 , includes a plurality of channels  7000  on each of the first and second platforms  6904  and  6908 , which receive identically shaped tongues (not shown) on the reverse side of the safety wall  6912 . When the first and second platforms  6904  and  6908  are moved apart to release the tongues from the corresponding set of channels, first and second cranes  5220  attach to respective attachment points on the safety wall  6912  and lower the safety wall  6912  into position on the desired side of the safety trailer  6900 . Unlike the embodiment of  FIGS. 51-52 , the attachment points are on the upper edge, and not on the sides, of the safety wall  6912 . When the wall is in the desired deployed position, dowels, or some other attachment mechanism, can be used to secure the safety wall  6912  to each of the first and second platforms  6904  and  6908 . 
     Slide Safety Wall Trailer Designs 
     In a number of safety trailer embodiments, the safety wall is deployed via a sliding mechanism, between the safety wall and safety trailer and/or between different segments of the safety wall. 
       FIGS. 59-60 and 72  depict a safety trailer according to an embodiment of this design. The safety trailer  5100  includes first and second platforms  5904  and  5908  and safety wall  5912  positioned between, and engaged with, the first and second platforms  5904  and  5908 . First and second segments  6000  and  6904  of the safety wall  5912  are interconnected by a matching tongue  7200  and groove  7204  mechanism as shown in  FIG. 72 . This mechanism permits the first and second segments  6000  and  6904  to move linearly, in the directions shown, relative to one another. In one configuration, independently operable brakes on the second platform are activated to hold the second platform stationary while the first platform is moved in the direction shown. When the safety wall  5912  is extended to the desired degree, dowels are inserted into holes  7208  passing from a backside of and through the safety wall segment  6900  and into the safety wall segment  6904 . In this manner, the dowels are inserted and removed from the protected work area. In one configuration, the wall length is adjustable by positioning a plurality of holes  7208  at selected intervals along a length of the safety wall  5912 , as shown in  FIG. 73 . In this manner, the safety wall is moved to the desired position, the holes in the wall segments  6900  and  6904  aligned, and dowels placed in the aligned holes. The edge  6040  may be beveled to reduce the likelihood of the edge becoming a snag to an impacting vehicle. 
       FIGS. 65-66  depict a safety trailer according to an embodiment of this design. The safety trailer  6500  includes first and second platforms  6504  and  6508  and safety wall  6512  positioned between, and engaged with, the first and second platforms  6504  and  6508 . The safety wall  6512  is secured to the first and second platforms by a matching tongue (not shown) and groove  6600  mechanism, such as that shown in  FIG. 72 . This mechanism permits the first and second platforms, when moved apart, to move, relatively to the safety wall  6512 , linearly, in the directions shown. In one configuration, independently operable brakes on the second platform are activated to hold the second platform stationary while the first platform is moved in the direction shown. 
       FIGS. 67-68  depict a safety trailer according to an embodiment of this design. The safety trailer  6700  includes first and second platforms  6704  and  6708  and safety wall  6712  positioned between, and engaged with, the first and second platforms  6704  and  6708 . First and second segments  6800  and  6804  of the safety wall  6712  are interconnected by a matching tongue  6808  and groove mechanism, such as that shown in  FIG. 72 . This mechanism permits the first and second segments  6800  and  6804  to move linearly, in the directions shown, relative to one another. The first and second segments  6800  and  6804 , while being movably (slidably) engaged relative to one another, are each fixidly or permanently engaged to a corresponding adjacent one of the first and second platforms  6704  and  6708 . In one configuration, independently operable brakes on the second platform are activated to hold the second platform stationary while the first platform is moved in the direction shown. 
     Safety Wall Structural Designs 
     A variety of safety wall structural designs will now be described. All of the designs shall be described with reference to a latitudinal cross section through the safety wall. These designs may be used for any of the safety walls discussed above. 
     Referring to  FIG. 41 , a safety wall  4100  according to an embodiment includes a plurality of spaced apart structural members  4104  extending into the page, with an outer skin  4108 . The outer skin  4108  faces traffic and provides the planar surface to direct impacting vehicles away from the protected area, located interiorly of the wall  4100 . The members  4104  define a two-dimensional matrix having multiple columns and rows of members. At each end of wall, an end plate (not shown) is connected to the members  4104 . As will be appreciated, the number and positioning of the members  4104  depend on the unique specifications and requirements of the application. 
       FIG. 42  depicts another safety wall embodiment. Unlike the embodiment of  FIG. 41 , the safety wall  4200  includes a single row of spaced apart structural members  4204  supporting an outer skin  4208 . 
       FIG. 43  depicts another safety wall embodiment. Unlike the embodiment of  FIG. 42 , the safety wall  4300  includes a single row of interconnected structural members  434  supporting an outer skin  4308 . 
       FIG. 44  depicts yet another safety wall embodiment. The safety wall  4400  includes the structural members  4304  and outer skin  4308  of  FIG. 43  but further includes force channeling members  4404 , structural members  4408 , and interior skin  4412  to dissipate any impacting force applied to the outer skin  4308 . As will be appreciated, the force channeling members  4404 , in one configuration, are gussets that direct some of the impacting force to the structural members  4408  and interior skin  4412 . 
     Other safety wall configurations may also be employed. By way of example, the safety wall configuration disclosed in copending U.S. application Ser. No. 12/533,931, filed Jul. 31, 2009; Ser. No. 12/347,458, filed Dec. 31, 2008; and Ser. No. 12/347,467, filed Dec. 31, 2008, each of which is incorporated herein fully by this reference. As will be appreciated, other features disclosed in these applications may be applied to any of the embodiments disclosed herein. 
     Other Features 
       FIG. 55  shows that a configuration of a safety wall  5500  that may be used with any of the above embodiments. Each end of the safety wall  5500  includes first and second elongated slots  5504  and  5508  at either end of the safety wall  5500 . The slots  5504  and  5508  receive a corresponding pin  5512 , which engages a corresponding one of the first and second platform. In the configuration shown, a pair of dowels  5520  is positioned between each end of the safety wall  5500  and a respective one of the first and second platforms. When the safety wall is not deployed, the dowels  5520  are in first positions  5530   a,b  and, when the safety wall is deployed, one set of the dowels  5520  nearest one edge is removed so that the other set of dowels  5520  become the axis of rotation of the safety wall, as discussed above. As the safety wall approaches a vertical orientation, the unremoved set of dowels  5520  move to second positions  5540   a  or  b . The length “L” of each slot determines a length of “drop” of the wall when the wall is deployed to a vertical orientation. In other words, if the length “L” is 2 feet, the pair of dowels on the lower edge of the deployed safety wall will move into the second position  5540   a  (assuming that edge  5550  is the lower edge and edge  5560  is the upper edge), causing the wall to move downwardly 2 feet. 
       FIGS. 74-76  depict various interlocking mechanisms that may be used with any of the above embodiments.  FIG. 74  depicts an interlocking set of grooves  7400  and teeth  7404  at the interface between a safety wall  7408  and platform  7412 . The interlocking set of grooves and teeth can not only provide structural strength to the interface but also provide a guide mechanism to align the safety wall  7408  and platform  7412 .  FIG. 75  shows the same interlocking mechanism used at the interface between two platforms when the safety wall is not deployed. In other words, when the safety wall is removed and the two platforms connected, the platform interfaces at either end of the wall are reverse images of each other, thereby permitting them to interlock to provide additional structural strength to the trailer. Thus, either end of the safety wall will have teeth and grooves that are also reverse images of each other to permit them to interlock with the opposing platforms.  FIG. 76  shows a similar interlocking mechanism for two adjoining safety wall segments. As will be appreciated, the mechanisms of  FIGS. 77-79  can also act as guide mechanisms to asset in positioning or aligning the adjacent safety wall segments, platform and safety wall, or platforms in a desired orientation relative to one another. 
       FIG. 32  depicts a safety trailer  3200  having a heavy roller  3250  on a second (rear) platform  3208 . The heavy roller  3250  may be used in lieu of or in addition to rubber tires. In one configuration, the rubber tires (not shown) are elevated above the road surface when the roller  3250  is in use (or in contact with the road surface), and the roller  3250  is elevated above the road surface when the rubber tires are in use (or in contact with the road surface). This may be effected, for example, by a hydraulically actuated mechanism as will be appreciated by those of ordinary skill in the art. The safety wall members  3220 , which are interconnected with one another and with the first and second platforms  3204  and  3208  are positioned on the bed defined by the first and second platforms. This safety wall embodiment is discussed in the various copending U.S. applications referenced above. When the safety wall is positioned between the first and second platforms  3204  and  3208 , the tractor  3280  pulls the safety trailer forward to provide a movable protected work area. The roller  3250  is lowered by engage the road surface in this mode. For asphalting operations in which hot asphalt decreases substantially the operational life of rubber tires, this configuration is of particular benefit. Additionally, the heavy roller  3250  can eliminate the need for a separate machine to compress the as applied asphalt. 
       FIG. 33  depicts a safety trailer according to another embodiment. The safety trailer  3300  includes an aggregate director  3350  to direct aggregate materials, such as dirt, gravel, and concrete into the protected work area, when the safety wall is in position. Examples of aggregate directors include hydraulically actuatable front dumps (which dump material forwardly rather than rearwardly or to the side), concrete chutes, concrete mixer, conveyors, and the like. 
     Any of the above trailer configurations and embodiments can have one or both of the platforms configured to include a rear caboose, as disclosed by U.S. Pat. No. 7,572,022, which is incorporated herein by this reference. 
     A number of variations and modifications of the invention can be used. It would be possible to provide for some features of the invention without providing others. 
     For example in one alternative embodiment, the features of the above embodiments may be combined with the features of other embodiments disclosed above. 
     In another alternative embodiment, the truck or tractor is incorporated into the safety trailer to provide a mechanized vehicle having a permanently connected safety wall. In this embodiment, the truck or tractor is not removably hitched to a safety trailer. 
       FIG. 80  shows an alternate embodiment for the safety trailer.  FIG. 80  is a view similar to the embodiment shown in  FIGS. 51-58 . As in  FIG. 80 , the trailer  8000  is shown in its unloaded or deployed configuration. The wall section  8010  has been removed from the loaded positions on top of the platforms  8020  and  8030  and connected between the platforms  8020  and  8030  to form a protective barrier  8040 . As can be seen in  FIG. 80 , the two ballast boxes  8050 , moveable along a fixed path, are placed on top of the platforms  8020  and  8030 . The ballast boxes provide a counter-balance to the weight of the wall section  8010 , which is disposed on the opposite side of the platforms  8020  and  8030 .  FIG. 80  shows a view of the safety trailer  8000  from the perspective of the protected work zone area. As can be seen, the safety trailer creates a protected work area  8060 , which includes a space adjacent to the wall section  8010  and between the platforms  8020  and  8030 . The road or other work surface is exposed within the work zone area  8060 . In the embodiment shown in  FIG. 80 , a crane with a hook  8070  is shown for lifting the wall section  8010  from the platforms  8020  and  8030  during assembly. 
     The present invention, in various embodiments, configurations, or aspects, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, configurations, aspects, subcombinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in various embodiments, configurations, and aspects, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments, configurations, or aspects hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and/or reducing cost of implementation. 
     The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the invention are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the embodiments, configurations, or aspects of the invention may be combined in alternate embodiments, configurations, or aspects other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the invention. 
     Moreover, though the description of the invention has included description of one or more embodiments, configurations, or aspects and certain variations and modifications, other variations, combinations, and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments, configurations, or aspects to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.