A drive-by methodology for the bridge deflection estimation based on the difference between two track geometries has been proposed. However, it does not apply to the section where the bridges of the same type are consecutive because it is difficult to evaluate the contribution of adjacent bridges. In this paper, numerical simulation targeting actual girders in long-scale bridges clarifies that the difference between two track geometries in the bridge consecutive section consists of a summation of one in each bridge section. Based on that, this paper proposes a simultaneous estimation method for each bridge deflection based on linear regression whose explanatory variable is the difference between two track geometries of each bridge, which can consider the contribution of adjacent bridges. On-site verification using five consecutive bridges indicates that the proposed method can estimate bridge deflection within 3% error unless its bearings do not have defects.