Culverts are essential under earth embankments to allow watercourses, such as streams and nallas, to pass through without obstructing the natural flow. They help manage floodwaters on both sides of the embankment, reducing water levels and mitigating flood risks. Culverts come in various shapes, including arch, slab, and box configurations, and can be constructed from materials such as masonry or reinforced concrete. Culverts, embedded within earth embankments, are subjected to traffic loads similar to those on the road and must be designed to accommodate these loads. This paper focuses on the structural design and parametric analysis of RCC box culverts, both with and without cushion. Design parameters such as size, invert level, and layout are determined based on hydraulic considerations and site conditions, with the cushion depending on the road profile at the culvert location. The study examines various load cases (e.g., empty box, full box, surcharge loads) and factors such as effective width, braking force, load dispersion through fill, impact factor, and earth pressure coefficient as per IRC codes. It provides a comprehensive discussion on code provisions, design considerations, and justifications for the structural design of RCC box culverts, ensuring they can withstand maximum bending moments and shear forces.