Abstract:
A rail track insert assembly for use in road-level railway crossings having a pair of rails secured to a rail bed, each of the rails having a gauge side and a field side, a rail base and an intermediate web and being adapted for limited vertical movement upon intermittent loading of the rail upon passage of a load on the rail, the assembly comprising a longitudinally extending flexible gauge side rail insert member having a top surface in the plane of the rail head and a bottom surface registering with the base of the rail, a rail-engaging side surface sealingly and fixedly registering with the web on the gauge side in order to move with the limited movement of the rail, and an opposite side surface including a planar surface inclined downwardly and outwardly away from the adjacent rail at a minor angle, a longitudinally extending center gauge panel comprising a rigid slab having a top planar road surface lying in the general plane of the top surfaces of the rails, a bottom surface engaging with the tie bed, and side surfaces including an inclined planar surface registering in tight compressive contact with the inclined planar surfaces of each of the first rail insert members when the rails are in unloaded condition and to register in looser compressive contact with each of the inclined planar surfaces of the insert member when the rail is in loaded condition.

Description:
This application is a continuation-in-part of application Ser. No. 08/847,982 filed Apr. 21, 1997, abandoned, which is a divisional of application Ser. No. 08/534,235 filed Sep. 26, 1995, now U.S. Pat. No. 5,622,312 issued Apr. 22, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to rail track surface structures and more particularly to a new and improved rail track surface structure employing resilient closure inserts between each side of the rails and adjacent road surfaces. 
     In rail track construction, it is frequently necessary to align the rail head with adjacent road surfaces. In heavy weight railway trackage, this occurs at level crossings, where vehicular roadways intersect railway trackage, and in light rail trackage in urban areas where street surfaces are aligned with rail head levels to facilitate pedestrian and vehicular movement. 
     Rails employed in both railway and light rail urban transport include a base, a vertical web, and a head portion; each pair of rails forming a track having inner sides designated “gauge” sides, facing each other, and outer sides designated “field” sides. 
     Rail design conventionally employed in railway trackage uses a T-rail section, generally symmetrical in cross-section, in which the flange of the railway wheel laterally engages the gauge side of the head portion of the rail, with no underlying engagement of the flange. However, for light rail transportation such as in typical urban light rail transportation systems, a girder-rail section is being increasingly employed, in which a flangeway is formed integrally in a gauge side lateral extension of the head of the rail, to accommodate the downwardly depending flange of the railcar wheel, the upstanding leg of the rail head so defining the flangeway then engaging the road surface between the rails to accommodate vehicular and pedestrian traffic. 
     It is with each of these rail designs that the present invention is concerned, as will be apparent as this disclosure proceeds. 
     Considerable effort and ingenuity has heretofore been displayed to improve rail track surface structures to reduce maintenance at the interface between rail and adjacent road surface. 
     Degradation of the structure results from water and solid particulate foreign matter (“detritus”) intrusion adjacent the rails, which passes downwardly to the rail bed, causing deterioration of the structure and frequent maintenance. 
     A further problem resulting from unwanted water intrusion into the rail bed results from the breakdown in the electrical insulation normally existing between the metal rail and the ground. In this regard, the rails are frequently employed as conductors of low-voltage currents used in signalling, or in applications of light rail transport in which the locomotive is electrically powered, the rail functioning as a conductor in the power circuit. Negative consequences result in stray currents escaping from the metal into surrounding structures or the ground, when water is permitted to intrude into the rail bed. The problem of water intrusion into the rail bed is further aggravated when dissolved road salts, entrained in the surface water, reach the metal in the rail bed, resulting in costly corrosion. 
     Conventionally, rail track surface structures have employed resilient electrically non-conductive inserts adapted for insertion in the space defined on both gauge and field sides of the rail members between the rails and the adjacent road surfaces, the purpose of which has been to attempt to seal the adjacent rail members from water and detritus while permitting the use of conventional asphalt materials between and against adjacent rails, on the gauge sides and field sides thereof, respectively. Typical of such level crossing inserts are those shown in U.S. Pat. No. 4,461,421 to Maass; U.S. Pat. No. 4,899,933 to Martin and U.S. Pat. No. 3,469,783 to Uralli, each of which discloses a railway crossing insert of resilient material, resting on the base of the rail, cooperating with the rail on the one side, and interfacing with the adjacent road surface on the other side. 
     Much of the sealing problem is occasioned by the necessary provision for accommodation of downward flexing of the rail and track bed consequent on the passage of heavy rail loadings from rail traffic. Such deflections are unavoidable and normally are of the order of several millimeters, which movement is largely manifest at the interface between the insert and the adjacent road surface, the insert itself moving with the rail. This rail and insert movement, however, is attendant with negative consequences, due to spalling, crumbling and cracking of the asphalt material on the adjacent road surface where it interfaces with the insert, requiring maintenance and restoration of the road surface. 
     Other problems in rail track surface structure insert design arise due to the necessity of providing sufficient support to the insert to stand up under automobile and truck traffic passing over the road level railway, causing such seals to break down. 
     It will be understood by those familiar with modern track construction, and particularly with light urban transit track, that tracks are frequently laid on a rail bed comprising steel track plates laid on concrete slabs, with electrical insulation between the base of the rail and the track plate; heavy rubber extrusions are usual for such purpose. 
     In such rail bed construction, known as “Direct Fixation”, the track plates are secured to the concrete slab by electrically insulated hold-down bolts set in the concrete slab; rail clips of the Pandrol (trademark) or similar type, flexibly secure the rail to the track plates underlying the electrical insulation, under downward spring biasing. 
     Further attention to insert design has been directed to modification of the bottom surface of the insert in order to accommodate such flexible rail clips used to secure the rail to the underlying track plates. Typical of such designs are those shown in U.S. Pat. No. 4,606,498 to Grant and U.S. Pat. No. 4,899,933 to Martin, each of which discloses means of relieving the undersurface of the insert adjacent the rail clips, thereby to form a chamber in order to accommodate the rail clips. 
     It will be recognized that the rail space between the rail members and the adjacent road surface will, in cross-section, be generally that of a truncated pyramid, having stepped sides, so dictated by the practical considerations of minimizing the width of the rail space at its top surface where exposure to surface traffic occurs, and increasing the width of the rail space at its bottom surface to accommodate the width of the rail base and rail securing clips. This generally truncated pyramidal cross-sectional shape dictates the design of the track surface structure insert assembly. 
     It is the object of the present invention to address and overcome each of these problems by providing a rail track surface structure for use in Direct Fixation track construction comprising insert members which adapt to both T-rail and girder rails, and accommodate vertical flexing of the rail relative to the adjacent road surface without resulting degradation of the adjacent road surface, while continuing to seal against the intrusion of water and solid detritus into the rail bed. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention comprises a rail track surface structure insert assembly comprising electrically non-conductive and flexible sealing assemblies for insertion in each of the gauge side and field side of the rail. In a first preferred embodiment, each insert assembly comprises a longitudinally extending first rail insert member sealingly registering with and contoured to fit against the head, web and base of the rail on each of its field side and gauge side; a longitudinally extending second offset insert member operatively interfacing with each of the first rail insert members at a generally vertical slippage plane formed therewith, while sealingly registering and interfacing with the adjacent road surface; and longitudinally extending support means cooperating with and supporting the second offset insert member and registering at its bottom surface with the underlying rail bed. 
     Each first rail insert member is extruded or moulded to a cross-sectional profile having a rail-engaging surface conforming to the adjacent surface of an adjacent rail, and an outer generally vertical planar surface registering with a corresponding planar surface of a cooperating second offset insert member, thereby defining a slip plane to permit relative movement of the first rail insert member with the second offset insert member consequent on the flexing of the adjacent track rail when under rolling load. 
     In the first preferred embodiment, the second offset insert member is formed to a cross-sectional profile having a rail side planar surface registering with the corresponding planar surface of the cooperating first rail insert member, and includes a downwardly and outwardly inclined leg portion resting at its bottom end on the rail bed, offset and sloping downwardly away from the adjacent rail, thereby spatially adapting to accommodate the underlying rail clips securing the adjacent rail to the rail bed by forming a chamber defined between the first and second insert members and the rail bed. The second offset insert member may optionally be formed having a significant thickness, of the same resilient material as that used in the first rail insert member, or alternatively may be formed of sheet metal or other relatively thin section material, as will be hereinafter described. 
     The third support means may optionally comprise a support member extruded or moulded to a cross-sectional profile configured at its upper surface to the underlying surface of the inclined leg portion of the second offset insert member, spatially occupying the volume underlying the downwardly and outwardly extending leg portion of the second offset member and overlying the adjacent rail bed, thereby to maintain the second offset insert member in close registering contact with the adjacent road surface and the cooperating first rail insert member. Alternatively, the support means may be formed integrally with the second offset member as a downwardly depending extension thereof, as will be hereinafter described. The third support member is longitudinally interrupted at intervals to accommodate the rail clips securing the rail to the track bed on each side of the rail, and is installed in short sections, spanning between adjacent rail clips. 
     Unlike the prior seals of this type, the present seal assembly provides a sealing system which permits flexing of the rail by accommodating relative movement of the first rail insert member against the second offset insert member along a slip plane defined at their vertical planar interface, without disengagement or relative movement of the second offset insert member with the adjacent road surface. 
     In a second preferred embodiment the second offset insert member comprises a panel member in the configuration of a rectangular prism having a planar edge surface registering with the corresponding planar edge surface of the cooperating first rail insert member, thereby to define a slip plane at their generally vertical planar interface in order to accommodate flexing of the rail. Such panel members may be pre-cast, to rest directly on the underlying rail bed, without any additional or third support means, and will form a major portion of the road surface adjacent the rail track. 
     In a third embodiment specifically intended for rail crossing installations, the slip plane of the second embodiment is modestly canted off vertical, downwardly and outwardly by approximately 5°, thereby to create a wedging action between the first rail insert member and the panel member at the slip plane on rebound of the rail upon its unloading, in order to promote tight engagement of the first rail insert member and the panel member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and understood by reference to the following description taken in connection with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a grade crossing according to the first preferred embodiment of this invention, the rails being of girder rail section; 
     FIG. 2 is an enlarged cross-sectional view in elevation taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is a partial enlarged cross-sectional view in elevation taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a partial enlarged cross-sectional view in elevation taken along line  4 — 4  of FIG. 1; 
     FIG. 4A is a perspective view of an alternative construction in which the first rail insert member is formed integrally with the third support insert member; 
     FIG. 5 is a perspective view of the first rail insert members for use in the structure depicted in FIGS. 1 through 4; 
     FIG. 6 is a perspective view of a second offset insert member for use in the structure depicted in FIGS. 1 through 4; 
     FIG. 7 is a perspective view of a third support insert member for use in the structure depicted in FIGS. 1 through 4; 
     FIG. 8 is an enlarged partial cross-sectional view in elevation depicting the insert assemblies of this invention used with a T-rail; 
     FIG. 9 is a cross-sectional view in elevation of the second preferred embodiment of the invention. 
     FIG. 10 is a partial enlarged cross-sectional view in elevation corresponding to the view of FIG. 3, depicting the third embodiment of the invention, in use with a T-rail and with precast panel. 
     FIG. 11 is an enlarged partial cross-sectional view in elevation showing an alternate embodiment; 
     FIGS. 12 and 13 are schematic cross-sectional views showing installation of the panel between the rails and the panels outside the rails. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As depicted in FIG. 1, the intersection of a railway track  10 , having a pair of steel rails  11 ,  11 ′ intersects with a vehicular road  12 . 
     The road  12  adjacent the track  10  is normally comprised of a rock base  13  on top of a subgrade  14  and a finish layer  15  which may be asphalt or concrete. Such a road construction abuts the field sides of the rails, FIG. 1, separated therefrom by the gap  16  which accommodates the insert assembly of this invention. Desirably, the road surface will extend as closely as possible towards the adjacent rail, in order to expose the maximum of road surface to vehicular traffic. 
     Rails  11 ,  11 ′ are supported on a sub-structure of which the base is concrete ties or a concrete slab, depicted at  17 , into which are set hold-down bolt assemblies  18 , depicted in detail in FIGS. 2 and 3. 
     Track plates  19 , drilled to accommodate the hold-down bolts  18 , rest on the concrete  10  slab or ties,  17 , and elastomeric pads  20 , underlying the bottom flange  23  of the rails  11 ,  11 ′ electrically insulate the metal rails from the ground. Pandrol (trademark) rail clips  22  secure the rails  11 ,  11 ′ to the track plates  19  by engagement with the bottom flange  23  of the rails as depicted in FIGS. 2 and 3. 
     The rails  11 ,  11 ′ of FIGS. 1,  2  and  3  are of the girder-type, having a flangeway  24  formed on the rail head  25  on its gauge side  26  opposed by its field side  27 . It will be understood that the flangeway  24  accommodates the downwardly depending flange of a railway wheel, not shown. 
     In FIGS. 2 and 3 may be seen the details of the profile of the insert members of a first preferred embodiment of this invention. Proceeding to describe the insert members in detail, reference will first be made to the pair of insert members abutting the rail, designated  30  and  40  respectively in FIGS. 2 and 3 which are designated herein as first rail insert members, one of which, designated  30 , is contoured and dimensioned to abut the field side  27  of the associated rail member, and is referred to in this disclosure as the “field side first rail insert member”, and the other of which is designated  40  and is referred to as the “gauge side first rail insert member”. The field side first rail insert member  30 , is formed having a rail engaging profile  31  on its rail side contoured and dimensioned to bear against the field side  27  of the adjacent rail  11 , having a top surface  32 , a side surface  33  contoured to fit snugly against the field side of the rail  11 , and a bottom surface  34  contoured to rest on the horizontally extending bottom flange  23  of the rail. 
     The gauge side first rail insert member  40  is similarly profiled on its rail side to bear against the outwardly extending flangeway on the gauge side of the rail, as depicted in FIG. 3 . 
     The field side  35  of the field side first rail insert member  30  and the gauge side  35  of the gauge side first rail insert member  40  are each provided with a planar vertical surface  36 ,  36 ′ respectively in FIGS. 2 and 3, which engages with a registering surface of the second offset insert member, as will be hereinafter explained, as this description proceeds. 
     A recess  37 , formed on the lower outside corner  38  of each of the first rail insert members  30 ,  40 , forms a longitudinal channel in the first rail insert member to accommodate the rail clip  22 , FIGS. 2 and 3 in overlying relationship. 
     The gauge side first rail insert member  40 , FIGS. 2 and 3 is contoured and dimensioned at its top surface  41  to register with the outwardly extending flange  24  on the gauge side  26  of the rail  11 . Otherwise, the flange side first rail insert member  40  in the embodiment for usage with the girder rail, is a mirror image in cross-section to the field side first rail insert member  30 , FIGS. 2 and 3, heretofore described in detail. 
     Turning now to a description of the second offset insert member of the first preferred embodiment of this invention, generally designated at  50 , FIGS. 2,  3  and  6 , this comprises a longitudinally-extending member having in cross-section, an upper vertical leg,  51 , a downwardly and outwardly inclined intermediate leg  52  and a bottom generally vertical leg  53 , formed in continuous section to provide a relatively thin-walled insert member to register with the adjacent road surface material such as the asphalt as depicted in FIGS. 1,  2  and  3 . The offset of the bottom vertical leg  53 , compared to the upper vertical leg  51 , will be such as to accommodate the rail clip  22  in cooperation with the recess  37  of the field side of the first insert member  30  and the gauge side of the first rail insert member  40  by defining a longitudinally-extending channel therefor, as described. At its lower extremity  54 , the second offset insert member  50  rests on the rail tie or rail bed slab  17 , as depicted in FIGS. 2 and 3, and at its rail-facing vertical planar surface  55  will register in closely engaging interfacing relationship with the planar vertical, surface  36  of the first rail insert members  30  and  40 , FIGS. 2 and 3, respectively, to define slippage planes A and B, again respectively, FIG.  3 . 
     Now turning to a description of the third support insert member of the first preferred embodiment of this invention, reference to FIG. 4 depicts a pair of trapezoidal cross-sections,  60  and  70 , being identical in mirror image, having a downwardly inclined upper surface  61 ,  71 , respectively, registering with the undersurface  56  of the second offset insert member  50 , as depicted in FIG. 4, thereby to afford underlying support thereto against the downward loading from the asphalt road material and surface vehicular traffic load applied to the upper extremity of the second offset insert member  50 . A generally vertical downwardly extending planar edge  62 ,  72 , respectively, registers with the adjacent bottom vertical leg  53  of the second offset insert member  50 , to provide lateral support thereto. A bottom planar surface  63 ,  73  respectively, rests on the underlying concrete tie or slab  17 , as depicted in FIG. 4, and a generally vertical planar inner face  64 ,  74  respectively, abuts the outer edges of the track plate  19  and bottom flange of the track. 
     Having thus described the insert members of the first preferred embodiment of this invention designed for a girder-type rail, attention will now be directed to a similar type of assembly for a T-type rail, for which reference is made to FIG.  8 . Since the T-rail is symmetrical in cross-section, the first rail insert members generally designated  130 ,  140 , and the second offset insert member  150 , and the third support insert member  160 , respectively, Y heretofore described in detail, will be similar in mirror image on the field side and the gauge side, except for the gauge recess  170 , formed on the gauge side of the first rail insert member  140  to accommodate the wheel flange of a rail car, not depicted. 
     In an alternative construction of the first preferred embodiment for this invention, the third support members  60 ,  70  of FIG. 4 are each forn˜ed integrally with the related second offset insert member, as depicted at  80  in FIG.  4 A. This integrally formed member comprises an upper vertical leg  81 , a downwardly and outwardly inclined road-supporting surface  82  and a downwardly extending lower portion  83  resting on the rail tie or road bed slab  17 . At its rail-facing vertical planar surface  84 , the member  80  will register in closely engaging interfacing relationship with the planar vertical surface  36 ,  36 ′ of each of the first rail insert members  30 ,  40  to define the slippage planes A and B, as heretofore described. In this alternative construction, assembly on-site is simplified in the elimination of a third member of the three separate insert components heretofore described, but on-site notching of the rail-facing sides of the member  80  may be required at its lower extremity in order to accommodate the rail clips  22 , FIGS. 2 and 3. In contrast, the third support members  60  and  70 , FIG. 4 in the first alternative embodiment are supplied in short lengths spanning between adjacent rail clips. 
     The first rail insert member  30 ,  40 ; the second offset insert member  50  and the third support insert member  60 ,  70 , are each depicted in perspective in FIGS. 5,  6  and  7  respectively. 
     The insert members are desirably extruded from a thermosetting mix of recycled rubber crumb and polyurethane resins. 
     In installation of the first alternative construction, each first rail insert member is positioned against the corresponding surface of the associated rail  11 ,  11 ′, following which third support insert members are positioned between members of each pair of rail clips  22 , and the sequence is completed by installation of the second offset insert member  50  in overlying relationship with the third support insert member and in edge-abutting relationship with the first rail insert member, as depicted in FIGS. 2,  3 ,  4  and  8 . The road surfacing material  15  is then placed snugly against the second offset insert member  50 , compressing its interfacing engagement at its vertical planar surface with the vertical planar surface  36 , of the registering first rail insert member. The upper surface of the first rail insert member, the upper surface of the second offset insert member and the adjacent asphalt road surface on each of the field side and the flange side of the rail are substantially even and level with the upper surface of the rail head  11  so as to present a uniform surface to vehicles and pedestrian traffic. 
     Downward deflection of the rails  11 ,  11 ′ resulting from railway car loading will be accommodated by slippage movement of the planar surface  36  of the rail insert members  30 ,  40  against the associated and registering planar surfaces of the adjacent second offset insert members  50  at the slip planes A and B, FIGS. 3 and 4. Subsequent unloading of the rail following passage of the railway car, permits the realignment of the first rail insert members at their upper surfaces in level engagement with the upper surface of the second offset insert members. 
     Thus, with the assembly of this invention as depicted and described in the first preferred embodiment, vertical deflection movement of the rail is confined to the interface between the first rail insert member and the second offset insert member, rather than the interface with the adjacent road surface. In this manner, the likelihood of crumbling, cracking and spalling of the road surface at its rail-facing edge is minimized or eliminated. 
     The close engagement of the planar edge surface of the first rail insert members with the corresponding planar edge surface of the associated second offset insert members, prevents the intrusion of water and detritus into the underlying rail bed. 
     In a second preferred embodiment of the invention, depicted in FIG. 9, the first rail insert members  30 ,  40 , interface at their respective planar vertical faces  36  with the planar vertical faces  261 ,  271  of a pair of road surface panels generally designated  262 ,  272  respectively, thereby defining the vertical slip planes designated A and B accommodating flexing movement of the rails and the cooperating first rail insert members  30 ,  40 , FIG.  9 . Each of the road surface panel members  262 ,  272  will provide a major portion of the track road surface, and is configured at its inward rail-facing edge in profile generally similar to the profile of the inward rail-facing edge of the second offset insert members  50 , FIG. 2, above described in detail. 
     At their bottom surfaces  263 ,  273 , the panels rest on the rail bed slab, as depicted in FIG.  9 . 
     It will be understood that in order to permit free flexing movement of the first rail insert members  30 ,  40 , relative to and against the road surface panels, the planar generally vertical faces of the panels must present a relatively smooth non-frangible surface at the slip planes A and B, FIG.  9 . 
     In a modification of the road surface panel depicted in FIG. 9, specifically intended for rail crossing installations, the generally vertical slip planes on the gauge sides of each of the rails  11 ,  11 ′, are inclined downwardly and outwardly away from the adjacent rail at a minor angle of approximately 5° to the vertical, as depicted in FIG. 10, thereby to create a wedging action between the panel member and the adjacent first rail insert member  70 , during installation and also upon rebound of the rail and first rail insert member following passage of the train and the consequent unloading of the rail. This wedging action functions to promote tight engagement of the first rail insert member with the adjacent stationary panel between the rails  11 ,  11 ′, which is enhanced during installation of the structure by horizontal compression of the first rail insert member against the adjacent rail. 
     In this modification, which is intended for railcrossing installations, the generally vertical configuration of the slip planes B, FIGS. 2 and 3, will be maintained on the field sides of each of the rails  11 ,  11 ′, in order to better accommodate vertical movement between the rail and field side roadway. 
     This modification which is shown in FIG. 10, optimally functions in the space between the interfacing rails, where a road surface panel is in engagement with the gauge sides of each rail in a pair of rails. The canted interface operates between the flexible insert member adjacent the rail and a centrally located panel. A feature of this embodiment is the compression maintained at the side surfaces of the center panel and the interfacing panel surfaces of the gauge side insert member. When the rail is in unloaded condition, this compression will be at a higher order of magnitude than when the rail is under load. Thus, when the rail is loaded with a downward force, the 5° incline reduces (but does not eliminate) the degree of compression at the interface, while still allowing continual contact at the angled interface, and restoration of the compression when the loading is relieved. This, continual compression serves to exclude the intrusion of detritus, water, snow and ice into the interface, and minimizes the effect of wear occurring at planar surfaces of the gauge side panel. FIG. 11 illustrates a cross-section of this in-place embodiment between a pair of rails  300 ,  302 . The panel  304  contacts the gauge side inserts  306 ,  308  at the slight minor angle as shown in FIG.  10 . 
     FIGS. 12 and 13 illustrate preferred steps for installation of the center panel  304  according to this embodiment. FIG. 12 shows the center panel which is first tilted for leverage from a hand-held instrument such as a flat-tipped long-handled pry-bar  310 , used to pry the elastomeric gauge side insert  308  away from the center panel and slightly compress the inserts  306  and  308  in order to permit the center panel  304  to drop into position between the rails. Then the prybar  310  is removed and the center panel  304  remains in place while the inserts  306 ,  308  remain in place and under compression. 
     FIG. 13 illustrates the next step in which a pair of field side panels  312 ,  314  are pushed into engagement against the field side rail inserts  316 ,  318 . 
     The road surface panels  312 ,  314  are of convenient rectangular configuration, and may be either preformed of concrete, or of poured-in-place concrete with suitable concrete forms to define the rail-facing edge surfaces described, and may be installed in rail trackage on the gauge side of each rail between members of a pair of rails or on the field side of rail members. 
     The rail insert members may be readily and economically formed by extrusion of comminuted used rubber stock obtained from discarded automobile tires, producing an elastomeric material having a Shore durometer rating of between about 65 and 70. Other non-rigid high molecular weight materials may alternatively be used, such as polyurethane, having good impact strength and resistance to abrasion, low coefficient of thermal expansion and chemical resistance, with high electrical insulating properties. 
     It will, of course, be understood that the insert assembly of this invention has application in both rail level grade crossings and in urban installation of light rail transit, where extensive sections of track are laid in street surfaces also used by motor vehicle and pedestrian traffic. 
     While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover such modifications and changes as fall within the true spirit and scope of the invention.