A guide rail assembly comprising a guide rail bracket assembly for connecting a car guide rail to a pair of left and right counterweight guide rails (106,108) in an elevator system, the guide rail bracket assembly comprising: a guide rail bracket for horizontally connecting the car guide rail to the pair of left and right counterweight guide rails (106, 108), the guide rail bracket comprising a first end portion for attachment to the left counterweight guide rail, a second end portion for attachment to the right counterweight guide rail, and an intermediate portion for attachment to the car guide rail; a first interface bracket for attaching the first end portion to the left counterweight guide rail, a second interface bracket for attaching the second end portion to the right counterweight guide rail, and a third interface bracket for attaching the intermediate portion to the car guide rail; and at least one of the first, second and third interface brackets (110a, 110b, 114) forms a connecting plate (142a, 142b, 130) for vertically connecting together adjacent guide rails; the guide rail assembly further comprising: a left counterweight guide rail attached to the first interface bracket; a right counterweight guide rail attached to the second interface bracket; and a car guide rail attached to the third interface bracket; wherein the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket; and characterized in that: in a pre-assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially parallel to the guide rail bracket, and in an assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially perpendicular to the guide rail bracket. a guide rail bracket for horizontally connecting the car guide rail to the pair of left and right counterweight guide rails (106, 108), the guide rail bracket comprising a first end portion for attachment to the left counterweight guide rail, a second end portion for attachment to the right counterweight guide rail, and an intermediate portion for attachment to the car guide rail; a first interface bracket for attaching the first end portion to the left counterweight guide rail, a second interface bracket for attaching the second end portion to the right counterweight guide rail, and a third interface bracket for attaching the intermediate portion to the car guide rail; and at least one of the first, second and third interface brackets (110a, 110b, 114) forms a connecting plate (142a, 142b, 130) for vertically connecting together adjacent guide rails; the guide rail assembly further comprising: a left counterweight guide rail attached to the first interface bracket; a right counterweight guide rail attached to the second interface bracket; and a car guide rail attached to the third interface bracket; wherein the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket; and characterized in that: in a pre-assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially parallel to the guide rail bracket, and in an assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially perpendicular to the guide rail bracket. a left counterweight guide rail attached to the first interface bracket; a right counterweight guide rail attached to the second interface bracket; and a car guide rail attached to the third interface bracket; wherein the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket; and characterized in that: in a pre-assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially parallel to the guide rail bracket, and in an assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially perpendicular to the guide rail bracket. in a pre-assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially parallel to the guide rail bracket, and in an assembled state, the first, second and third interface brackets (110a, 110b, 114) are attached to the guide rail bracket and to the guide rails (104, 106, 108) such that the guide rails run substantially perpendicular to the guide rail bracket.