A precast traffic barrier configured for assembly on a top portion of an underlying concrete earth retaining wall, comprising a cantilever triangular stem, the cantilever triangular stem comprising: a front portion comprising a front surface (120,130), a rear surface, a top surface, and a bottom surface; a horizontal stem extending outwardly from the rear surface of the front portion, the horizontal stem comprising at least a vertical center portion, a left protrusion and a right protrusion; a diagonal portion connecting the rear surface of the front portion to the horizontal stem; an alignment seat extending along at least a portion of the horizontal stem, wherein: the left protrusion extends outwardly from a bottom left side of the vertical center portion of the stem; the right protrusion extends outwardly from a bottom right side of the vertical center portion of the stem; the left protrusion is triangular to the right protrusion; the diagonal portion extends directly above the vertical center portion in a vertical plane defined by the vertical center portion and the alignment seat is, in installed condition of the precast traffic barrier, connected to at least: the top portion of the underlying earth retaining wall; the rear surface of the front portion; a bottom face of the left protrusion; and a bottom face of the right protrusion; characterized in that the front portion further comprises a slanted portion at its rear surface configured for vehicular impact when the barrier is installed. a front portion comprising a front surface (120,130), a rear surface, a top surface, and a bottom surface; a horizontal stem extending outwardly from the rear surface of the front portion, the horizontal stem comprising at least a vertical center portion, a left protrusion and a right protrusion; a diagonal portion connecting the rear surface of the front portion to the horizontal stem; an alignment seat extending along at least a portion of the horizontal stem, wherein: the left protrusion extends outwardly from a bottom left side of the vertical center portion of the stem; the right protrusion extends outwardly from a bottom right side of the vertical center portion of the stem; the left protrusion is triangular to the right protrusion; the diagonal portion extends directly above the vertical center portion in a vertical plane defined by the vertical center portion and the alignment seat is, in installed condition of the precast traffic barrier, connected to at least: the top portion of the underlying earth retaining wall; the rear surface of the front portion; a bottom face of the left protrusion; and a bottom face of the right protrusion; characterized in that the front portion further comprises a slanted portion at its rear surface configured for vehicular impact when the barrier is installed. the left protrusion extends outwardly from a bottom left side of the vertical center portion of the stem; the right protrusion extends outwardly from a bottom right side of the vertical center portion of the stem; the left protrusion is triangular to the right protrusion; the diagonal portion extends directly above the vertical center portion in a vertical plane defined by the vertical center portion and the alignment seat is, in installed condition of the precast traffic barrier, connected to at least: the top portion of the underlying earth retaining wall; the rear surface of the front portion; a bottom face of the left protrusion; and a bottom face of the right protrusion; characterized in that the front portion further comprises a slanted portion at its rear surface configured for vehicular impact when the barrier is installed. the top portion of the underlying earth retaining wall; the rear surface of the front portion; a bottom face of the left protrusion; and a bottom face of the right protrusion; characterized in that the front portion further comprises a slanted portion at its rear surface configured for vehicular impact when the barrier is installed.