12. (15 points) The Alabama crash data show that a stop-controlled intersection in Tuscaloosa has an average of 15 crashes per year. This stop-controlled intersection is causing excessive delays during

peak hours. The City plans to convert the intersection into a roundabout which is often associated with a greater operational efficiency than a stop-controlled intersection. Before the conversion, the City wants to know whether the project can also improve the safety. If yes, please calculate the number of crashes that could be reduced by this project.