Istanbul Strait is one of the most important and dangerous maritime passage in the world. In this study, the hazards for a possible collision accident between the ships passing through the Istanbul Strait from north-south direction and the local ferries crossing the strait from east-west direction were investigated by using a simulation modeling. The purpose of this work is to define the hotspots for encounters and calculate the probability of collisions between these ships. This calculation is triggered by a search on the effect of schedule changes of the ships in passage to the number of ship crossings on these hotspots. In this study, it is found that the management of the passage schedule can be effective for a significant increase and decrease in the collision probability. As a conclusion, the collision probability which causes a risk was assessed for Istanbul Strait and the schedule change as a risk reduction option was evaluated.