The train will partly burned,but the whole train will be cleared by bulldozer later
So your improvement is that instead of automatically scrapping and clearing the tracks, you have to scrap mostly undamaged wagons manually?
It may improve aesthetics in the collision, but I don't think it's an improvement in game play. Also, isn't it unrealistic that you scrap perfectly fine engine or wagons? Normally, a transport company would re-assemble the train in a depot, and use it for the remainder of its lifetime.
So it seems to me you fixed one unreality, and replaced it by an additional manual action, and added more unrealism one step further in the chain of events. With respect to realism the program remains equally broken if not worse. (Now, the train is completely burned, making it logical that it is entirely non-functional and scrapping is the only option. In your proposal, you have to scrap perfectly fine looking wagons without logical reason of any kind, it's not explainable to a user why he has to do that.)