What’s the idea

Mechanism which would not allow the bus to move if people are standing on its stairs, thereby preventing accidents

Santhosh observed this problem everyday commuting from his village to his school and thought about this idea. He finds Physics quite easy and wants to pursue aeronautical engineering and take up space research. Nivashini likes reading story books and wants to become a doctor. Rajasekar likes outdoor sports, participates in NCC and would like to become an IPS officer while Rathna, who also likes reading books wants to become a teacher.