When a train runs in a tunnel, air pressures generate stresses on the car body and glass windows. To study these effects, we collected field test data and simulated the internal pressures of narrow-gauge railway cars. Then we analyzed the relation between the air pressures generated outside and inside the train and stresses on the car body and glass panels. We also estimated the effect on the car body. In relation to internal pressure of cars, we proposed a model to simulate and calculate the internal pressure of cars. We found an equivalent hole area of car body to alleviate aural discomfort.