A cost-effective technique is presented to determine the dynamic factor of reinforced concrete deck slab through experiment, simulations, and statistical method. The experiments were conducted on a one-fourth scale prototype model of a pre-existing railway bridge deck slab of size 645 × 565 × 86 mm against static and transient dynamic loading. The average measured experimental peak force from the static and transient dynamic tests was found to be 99 and 145.7 kN, respectively. A numerical simulation was conducted to evaluate the dynamic factor using ABAQUS finite element software. It was observed that the results obtained from simulations were in confidence with the experimental results as well as codal provisions, and the dynamic factor obtained from the experiment and simulation was found to be 1.47 and 1.52, respectively. Further, the influence of length of deck slab, mass, and velocity of impactor on the prediction of the dynamic factor using a finite element analysis and statistical method was studied. The statistical model was performed in terms of regression equation using Response Surface Methodology and the section offering maximum resistance which were optimized using the analysis of variance. The predicted response of deck slab in terms of impact force through finite element simulations was compared with the statistical approach. Overall, it was observed that the predicted peak impact force is found in good agreement with the statistical method. It was concluded that the 4.58 m span was found to be offering highest resistance against 8.1 m/s velocity with the mass of 14.53 tons among the various chosen cases, and the most conservative value of dynamic factor was found to be 2.81 and 2.74 through statistical method and FE simulations, respectively. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.