A road traffic accident happens when something goes wrong on the road and people or things (like cars or bikes) crash into each other. It's like when you are playing with your toy cars and they crash into each other accidentally.
Sometimes, road traffic accidents happen because people make mistakes while driving, like not paying attention or breaking the rules of the road. Other times, accidents can happen because of things like bad weather or car problems.
When a road traffic accident happens, it can be very dangerous and scary. People can get hurt, and sometimes cars can be damaged so badly they can't be fixed. It's important to always be careful and follow the rules of the road when you're driving or walking near roads to avoid accidents.