Local and intensive short bursts of heavy rain which may cause sudden hazards such as unexpected flooding are becoming more frequent in Japan. Moreover, these rains may be causing heavy rain to fall only over a limited area which may be narrower than the distance between rain gauges along railway lines. Therefore, current safety measures of train operation based on observation data measured by these gauges may not work well for these hazards. To address this problem, we developed a system that assists train stop and assists passenger evacuation to avoid those hazards. In this paper, first, we mainly describe the calculation algorithm and functions of the system. Next, we carry out simulations to confirm the validity and accuracy of calculations made by the system.