Disclosed herein are embodiments of a roadside barrier segment to sit on top of a retaining wall to provide impact resistance to vehicular traffic. Concrete traffic barriers are pre-cast in a controlled manufacturing environment then transported as a modular precast concrete segment to the jobsite and installed interlocking directly on top of an earth retaining wall. The precast concrete segment is designed to have a counterweight from soil backfill on a stem of the precast segment that resists overturning pressures from vehicle impact on the traffic barrier segment that extends above the roadway surface. The stem may be triangular in shape to capture more of the backfill soil. A vertical node may be placed on one side of the segment and a receiving channel on the opposite side of the segment to allow the interaction of adjacent segments to share impact loads from motor vehicles.

CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. provisional application entitled, “Precast Traffic Barrier Segment Atop Retaining Wall System,” having application No. 61/766,794, filed Feb. 20, 2013, and U.S. provisional application entitled, “Precast Leveling Segment Below a Traffic Barrier Atop an Earth Retaining Wall System,” having application No. 61/914,127, filed Dec. 10, 2013, and, both of which are entirely incorporated herein by reference. 
    
    
     BACKGROUND 
     Precast concrete earth retaining walls are commonly used for architectural, site development and roadway/highway construction applications. When roadways are located above or rest on top of the completed earth retaining wall, a traffic barrier segment is required to prevent vehicles from falling off of the retaining wall. Therefore, a traffic barrier segment is required to contain the impact from vehicles to keep them from falling over the retaining wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a view of the exemplary precast traffic barrier segment in accordance various first embodiments of the disclosure; 
         FIG. 2  is a cross sectional view of an earth retaining wall with the exemplary precast traffic barrier segment of  FIG. 1  sitting on top of an earth retaining wall in accordance various embodiments of the disclosure; 
         FIG. 3  is an elevation view of an earth retaining wall with the exemplary precast traffic barrier segment of  FIG. 1  making up the top row of precast concrete segments in accordance various embodiments of the disclosure; 
         FIG. 4  is a side view of the exemplary precast traffic barrier segment of  FIG. 1  in accordance various embodiments of the disclosure; 
         FIG. 5  is a top view of the exemplary precast traffic barrier segment of  FIG. 1  in accordance various embodiments of the disclosure; 
         FIG. 6  is a back view of the exemplary precast traffic barrier segment of  FIG. 1  in accordance various embodiments of the disclosure. 
         FIG. 7  is a view of the exemplary precast traffic barrier segment that interact with adjacent segments in accordance various second embodiments of the disclosure; 
         FIG. 8  is a cross sectional view of an earth retaining wall with the exemplary precast traffic barrier segment of  FIG. 7  that interact with adjacent segments sitting on top of an earth retaining wall in accordance various embodiments of the disclosure; 
         FIG. 9  is an elevation view of an earth retaining wall with the exemplary precast traffic barrier segment of  FIG. 7  that interact with adjacent segments making up the top row of precast concrete segments in accordance various embodiments of the disclosure; 
         FIG. 10  is a side view of the exemplary precast traffic barrier segment of  FIG. 7  that interact with adjacent segments in accordance various embodiments of the disclosure; 
         FIG. 11  is a top view of the exemplary precast traffic barrier segment of  FIG. 7  that interact with adjacent segments in accordance various embodiments of the disclosure; 
         FIG. 12  is a back view of the exemplary precast traffic barrier segment of  FIG. 7  that interact with adjacent segments in accordance various embodiments of the disclosure 
         FIG. 13  is a view of the exemplary precast leveling segment in accordance various first embodiments of the disclosure; 
         FIG. 14  is a cross sectional view of an earth retaining wall with the exemplary precast leveling segment of  FIG. 13  sitting as the top course of an earth retaining wall in accordance various embodiments of the disclosure and just underneath the traffic barrier course; 
         FIG. 15  is an elevation view of an earth retaining wall with the exemplary precast leveling segment of  FIG. 13  making up the second from the top row of precast concrete segments in accordance various embodiments of the disclosure; 
         FIG. 16  is a side view of the exemplary precast leveling segment of  FIG. 13  in accordance various embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein various embodiments of precast traffic barrier segments that are designed to rest above an earth retaining wall of precast segments to prevent traffic from falling over the retaining wall. The objective of the current invention is to allow a uniform height precast traffic barrier be installed parallel and to the alignment grade of the proposed roadway grade above the wall even though the supporting retaining wall is constructed and installed in parallel uniform height segments along courses of modular precast units. In order to provide a differing height required to follow a roadway grade that varies along the wall length especially in vertical curves of the changing roadway grade, a leveling or variable height course of modular concrete segment block units is required. The current invention, with the use of a tilting table to cast the leveling units at various heights/angles, modifies the immediate course below the uniform height traffic barrier course to allow the traffic barrier to follow the changing vertical grade of the roadway. 
     When roadways, driveways or vehicle access is planned above an earth retaining wall, a barrier to prevent traffic from falling over the walls leading edge is typically required. Traditionally, a guard rail or poured in place concrete traffic barrier segment is installed above the retaining wall to contain vehicles above the earth retaining wall in the planned drive isle or roadway. The exemplary embodiments expedite installation of the traffic barrier segment by making it a part of the earth retaining wall system where the barrier segment can act as the top row of modular precast retaining wall system and provide resistance to overturning by using the backfill soil weight resting on the horizontal triangular stem. The downward pressure of the soil backfill beside and on top of the horizontal stem provides the resisting pressure to have the exemplary precast traffic barrier segment act as a cantilever foundation/vertical wall and resist impact loads from vehicles on the portion of the barrier segment extending above grade. 
     Generally speaking, the portion of the traffic barrier segment extending above grade has a shape that varies depending upon a state's rules and regulations (promulgated by the Department of Transportation), which define certain acceptable geometries and dimensions for barrier segments installed along roadways/highways of the state. Therefore, the geometry of the traffic barrier segment's vertical portion extending above roadway grade may vary from state to state. 
     First Embodiment(s) 
     Referring to  FIG. 1 , an exemplary precast traffic barrier segment  100  has a vertical face  130  that extends above roadway grade and a face  120  extending below roadway grade that consists of the upper portion of the underlying earth retaining wall. The top of the barrier segment portion  140  above roadway grade is typically 32 inches above the roadway or driveway surface elevation. The back face of the barrier segment extending above grade is 180 where the vehicular impact would occur as well as the slanted portion  150 . The overall stability of the exemplary precast traffic barrier segment is prevented from overturning by a counterweight from backfill soil resting beside and above the rear stem  190 . A triangular portion  110  of the rear stem helps capture the surrounding backfill soils weight to add resisting force by means of downward weight on the exemplary traffic barrier segment stem  190 . The top of the stem  160  is approximately 30 inches below the drive or roadway grade to allow the installation of utilities and pavement section not obscured by the precast traffic barrier segment piece or segment. 
       FIG. 2  shows a cross section  200  of the elevated roadway grade  220  sitting on top of the earth retaining wall. The stem  190  of the exemplary precast traffic barrier segment sits well below the pavement grade  220  to prevent interference. To keep the exemplary precast traffic barrier segment from sliding on top of the retaining wall, two protruding lugs  170  extend below the exemplary traffic barrier segment to lock into the top concrete precast segment of the earth retaining wall. For installation of the exemplary precast traffic barrier segment, a square hole  240  is cast into the exemplary precast traffic barrier segment to facilitate lifting and hoisting into place. A diagonal portion of the stem  210  is required to transfer the downward cantilever pressure on the stem  190  to the vertical portion of the exemplary precast traffic barrier segment to prevent impact on the face  120  of the barrier segment facing vehicular traffic. 
     In looking at an elevation view,  FIG. 3 , of the front face of the earth retaining wall, the exemplary precast traffic barrier segment  100  makes up the top row of the concrete earth retaining wall to complete or top out the earth retaining wall soil retention requirements. The grade of the proposed roadway  220  is below the barrier segment portion of the precast traffic barrier segment but above the stem portion  190  of the traffic barrier segment. 
     In  FIG. 4 , the exemplary precast traffic barrier segment  100  is shown to illustrate the unique features. The lower locking lugs  170  extend below the bottom of the stem  190  to lock into the earth retaining wall system below. The front face  120  of the precast traffic barrier segment is in vertical alignment with the underlying retaining wall face to complete the earth retaining wall vertical plane alignment.  FIG. 5  shows the top view to illustrate the triangular sides  110  of the stem  190  cover approximately 50% of the overall counterweight area of backfill soil that is available to provide weight for overturning resistance. The triangular stem portions  110  allow the reduced horizontal coverage area and hence save precast concrete area/volume. 
       FIG. 6  is a rear view of the exemplary precast traffic barrier segment  100  which shows the diagonal connection arm  210  from the top of the stem  160  up to the vertical portion of the traffic barrier segment  180  and  150 . 
     It should be emphasized that the above described invention of the present disclosure is to implement an arching effect within the earth retaining wall backfill soils by the triangular stem to take advantage of the soil backfill vertical weight to provide resisting force from horizontal vehicular impact on the portion of the stem above the drive isle or roadway grade. The dimensions of the portion of the barrier segment above grade may vary depending upon various Department of Transportation guidelines for impact barrier segments along roadways. 
     Second Embodiment(s) 
     When roadways are located above or rest on top of the completed earth retaining wall, a traffic barrier segment may be required to handle large impact loads from trucks or other large vehicles. The results may be more pressure than the individual segments can resist from overturning and sliding. Therefore, the attachment of one segment to the next horizontally in order to share the impact load may be required. In this instance, a groove is cast in the side of the segment with a slip joint to allow the segments to work together in resisting the impact. 
     The exemplary embodiment allows the individual segments to carry more impact load by interacting with the adjacent segments to provide more resistance than any one segment can exhibit alone. Also, the grove is such that when setting the segments in place, the adjacent segment slides down over the top to expedite installation of these traffic barrier segments. Also, the groove allows the alignment of the segments to be kept in line so the segments do not protrude out from one another that could snag a vehicle that comes in contact with the wall and slides down the traffic barrier segment impacting several segments in series. 
     Referring to  FIG. 7 , the exemplary precast traffic barrier segment  300  has a vertical face  330  that extends above roadway grade and a face  320  extending below roadway grade that consists of the upper portion of the underlying earth retaining wall. The top of the barrier segment portion  340  above roadway grade is typically 36 inches above the roadway or driveway surface elevation. The back face of the barrier segment extending above grade is 380 where the vehicular impact would occur as well as the slanted portion  350 . The overall stability of the exemplary precast traffic barrier segment is prevented from overturning by a counterweight from backfill soil resting beside and above the rear stem  390 . A triangular portion  310  of the rear stem helps capture the surrounding backfill soils weight to add resisting force by means of downward weight on the exemplary traffic barrier segment stem  390 . The top of the stem  360  is approximately 30 inches below the drive or roadway grade to allow the installation of utilities and pavement section not obscured by the precast traffic barrier segment piece or segment. A vertical node  430  protrudes out the side of the segment to fit into the adjoining segments groove  440  to allow interconnectivity. The groove does not extend all the way to the top of the segment but terminates at  450  to not expose the joint and hide from view. 
       FIG. 8  shows a cross section  400  of the elevated roadway grade  420  sitting on top of the earth retaining wall. The stem  390  of the exemplary precast traffic barrier segment sits well below the pavement grade  420  to prevent interference. To keep the exemplary precast traffic barrier segment from sliding on top of the retaining wall, two protruding lugs  370  extend below the exemplary traffic barrier segment to lock into the top concrete precast segment of the earth retaining wall. For installation of the exemplary precast traffic barrier segment, a square hole  420  is cast into the exemplary precast traffic barrier segment to facilitate lifting and hoisting into place. A diagonal portion of the stem  410  is required to transfer the downward cantilever pressure on the stem  390  to the vertical portion of the exemplary precast traffic barrier segment to prevent impact on the face  380  of the barrier segment facing vehicular traffic. The vertical slot  440  receives the adjacent vertical node  430  to interlock and allow connectivity and shared resistance when impacted. 
     In looking at an elevation view,  FIG. 9 , of the front face of the earth retaining wall, the exemplary precast traffic barrier segment  300  makes up the top row of the concrete earth retaining wall to complete or top out the earth retaining wall soil retention requirements. The grade of the proposed roadway  420  is below the barrier segment portion of the precast traffic barrier segment, but above the stem portion  390  of the traffic barrier segment. The segments connect horizontally by a node and vertical channel  460  to share impact loads from vehicles. 
     In  FIG. 10 , the exemplary precast traffic barrier segment  300  is shown to illustrate the unique features. The lower locking lugs  370  extend below the bottom of the stem  390  to lock into the earth retaining wall system below. The front face  320  of the precast traffic barrier segment is in vertical alignment with the underlying retaining wall face to complete the earth retaining wall vertical plane alignment. The vertical slot  440  is to receive the vertical node from the adjacent segment.  FIG. 11  shows the top view to illustrate the triangular sides  310  of the stem  390  cover approximately 50% of the overall counterweight area of backfill soil that is available to provide weight for overturning resistance. The triangular stem portions  310  allow the reduced horizontal coverage area and hence save precast concrete area/volume. The vertical node  430  extends out the side of the segment to fit inside the adjacent segments vertical slot  440 . 
       FIG. 12  is a rear view of the exemplary precast traffic barrier segment  300  which shows the diagonal connection arm  410  from the top of the stem  360  up to the vertical portion of the traffic barrier segment  380  and  350 . The vertical node  430  is shown as well as the receiving vertical slot or channel  440 . 
     It should be emphasized that the second embodiment implements an arching effect within the earth retaining wall backfill soils by the triangular stem to take advantage of the soil backfill vertical weight to provide resisting force from horizontal vehicular impact on the portion of the stem above the drive isle or roadway grade. The dimensions of the portion of the barrier segment above grade may vary depending upon various Department of Transportation guidelines for impact barrier segments along roadways. The vertical node on one side and vertical slot or channel on the opposite side allows horizontal interaction of adjacent segments to share vehicle impact loads. 
     Third Embodiment(s) 
     Referring to  FIG. 13 , shown is an exemplary precast leveling segment  500 . The precast leveling segment  500  has a front portion  320 , horizontal stem  590 , and an alignment seat  165 . The front portion  320  comprises a front surface  530 , a rear surface  535 , a top surface  540 , and a bottom surface  545 . The top surface  540  may slope in parallel to an above roadway. The bottom surface  545  is parallel to an underlying earth retaining wall. For example, the top surface  540  may run parallel to a roadway above the precast leveling segment  500  that slopes from the left side  560  to the right side  550  whereas the bottom surface  545  may run parallel to an underlying earth retaining wall that does not slope. In this example, the top surface  540  is not parallel to the bottom surface  545  but the bottom surface  545  is perpendicular to the front surface  530 . Continuing the example, the height of the left side  560  is greater than the height of the right side  550  to facilitate the top surface  540  running parallel to the roadway above. Allowing the top surface  540  to run parallel to the roadway and the bottom surface  545  to run parallel to the underlying earth retaining wall prevents the need to slope the underlying earth retaining wall. 
     The horizontal stem  590  extends outwardly from a rear surface  535  of the front portion  320 . The horizontal stem  590  comprises a triangular portion  310  extending left and right from the top surface  570  of the horizontal stem  590 . The triangular portion  310  of the horizontal stem  590  helps capture the weight of the surrounding backfill soil to add resisting force by means of downward weight on the precast leveling segment  500 . Two open boxed cavities  520  are cast into the lower section of the precast leveling segment  500  to allow lifting for placement. The alignment seat  165  has right and left aligning elements  370  that align the leveling segment to an underlying earth retaining wall. 
       FIG. 13  depicts an isometric view to illustrate that the triangular portion  310  of the horizontal stem  590  covers approximately 50% of the overall area of backfill soil that is available to provide weight for overturning resistance. The triangular portion  310  allows a reduced horizontal coverage area and saves precast concrete area and/or volume. 
     In reference to  FIG. 14 , a cross section  600  of a sloping elevated roadway grade  420  is shown sitting on top of an earth retaining wall. The elevated roadway grade  420  slopes toward the viewer of  FIG. 14 . The top surface  540  of the front portion of the precast leveling segment  500  slopes toward the viewer of  FIG. 14  parallel to the elevated roadway grade  420 . One of two protrusions  170  is shown. The protrusion  170 , along with the other, nonvisible protrusion, locks into the precast segment below. A horizontal stem  590  comprises at least a triangular portion  310  and square holes  240 . For installation of a precast leveling segment  500 , two square holes  240  are cast into the precast leveling segment  500  for lifting and hoisting the precast leveling segment  500  into place. A horizontal stem  590  parallel to the traffic barrier above is required to transfer downward vertical pressure from a traffic barrier above to the horizontal stem  590  below the precast leveling segment  500 . 
       FIG. 15  depicts an elevation view of the front face of the earth retaining wall. A leveling course  505  of precast leveling segments  500   a ,  500   b , and  500   c  makes up the designated row below the elevated roadway grade  420 . Although many precast leveling segments are depicted, the leveling course  505  may comprise one or more precast leveling segments. The top surfaces  540   a ,  540   b , and  540   c  of the precast leveling segments  500   a ,  500   b , and  500   c  slope parallel to the sloping elevated roadway grade  420 . Thus, the front surface heights of left edges  560   a ,  560   b , and  560   c  and right edges  550   a ,  550   b , and  550   c  of each of the precast leveling segments  500   a ,  500   b , and  500   c  may increase or decrease relative to the precast leveling segments  500   a ,  500   b , and  500   c  immediately to the left or right as the elevated roadway grade  420  increases or decreases. The precast leveling segments are in an order that maintains a predefined distance between the elevated roadway grade  420  and the top surfaces  540   a ,  540   b , and  540   c . For example, the distance between a point at the top of the left edge  560   a  and a point  422   a  on the roadway that is on a line parallel to the left edge  560   a  equals the distance between a point at the top of the right edge  550   a  and a point  422   b  on the roadway that is on a line parallel to the right edge  550   a . In one embodiment, the first front surface height of the right edge  550   a  of a first precast leveling segment  500   a  is greater than a second front surface height of the right edge  550   b  of a second precast leveling segment  500   b . Therefore, the top surfaces  540   a  and  540   b  slope parallel to the elevated roadway grade  420  above the leveling course  505 . The precast leveling segments  500   a ,  500   b , and  500   c  are aligned such that the height of the right edge  550   a  of the first precast leveling segment  500   a  is within a predefined delta of the height of the left edge  560   b  of the second precast leveling segment  500   b  to ensure a gradual slope parallel to the elevated roadway grade  420  above. In alternative embodiments, the height of the left edge  560   b  may be greater than the height of left edge  560   a  when the elevated roadway grade  420  increases slope or the height of the left edge  560   b  may be less than the height of left edge  560   a  when the elevated roadway grade  420  decreases slope. 
     In  FIG. 16 , a side view of a precast leveling segment  500  is shown. Shown is a front portion  520 , horizontal stem  590 , and alignment seat  515 . The front portion  530  comprises a front surface  525 , a top surface  540 , a rear surface  535 , and a bottom surface  545 . The horizontal stem  590  attaches to the rear surface  535  of the front portion  520 . The top surface  540  slopes downward, with a greater height of the left edge  560  than the height of the right edge  550 . The horizontal stem  590  comprises a top surface  570  and a triangular portion  310 . Two square holes  520  are cast into the horizontal stem  590  of the precast leveling segment  500  for lifting and hoisting the precast leveling segment  500  into place. The alignment seat  515  comprises at least lower aligning elements  370  that extend below the horizontal stem  310  to lock in to the earth retaining wall system below. The lower aligning elements  370  may be locking lugs. 
     It should be emphasized that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are merely possible non-limiting examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention.