Structural health monitoring for the effective maintenance of railway structures using moving trains has been rapidly advancing. Bridge deflection is a basic performance index of bridges and one of the targets of structural health monitoring. A bridge deflection estimation method based on the longitudinal level of track geometry measured by 2-bogies type track inspection vehicles, which are widely used in Japanese local railroads, has been previously proposed. However, evaluating track geometries caused by the deflections of adjacent bridges remains a challenge. Herein, mutual effects of the deflections of adjacent bridges are evaluated using a bridge deflection-track geometry transformation program based on finite element modeling. The obtained results indicate that the track geometry independently affects the deflection of each bridge. Hence, the summation of the track geometries of each bridge can be used for estimating bridge deflection, even in the case of consecutive bridges.