The prefabricated bridge is common method in construction since it provides controlled environmental conditions and long-term durability. These adjacent precast box beams are placed side by side with 15mm gaps, the top flanges connected with longitudinal shear keys poured on-site to assist in truckload distribution. Since the concrete-filled joints provide transverse shear rigidity, the load transferred from one beam to another takes place through transverse shear. A parametric study is conducted to investigate the accuracy of simplified analysis method in CHBDC for shear-connected beams to the adjacent box beams. A 3D finite-element was conducted on a wide range of box beams to obtain their magnification factors for moment and shear when subjected to truck loading. The obtained results were correlated with CHBDC and a more reliable simplified equations for distribution factors was developed. Special attention was given to the limitations of CHBDC simplified method and how it can be revised to include the adjacent box-beam.