Safety elevator door / elevator

We sometimes experience or see accidents that a hand gets caught between elevator doors. This accident can happen while unconsciously putting a hand on elevator doors— getting hurt as the hand is caught between the doors when they open. And this kind of accident happens most frequently to children. If children put their hands on elevator doors, their hands get pulled inside the gap between the doors when they open. Such behavior leads to the accident that their hands get caught in the gap, and they get harmed— getting bruises, scars, or fractures. With the existing signs of warning, there is a limit to solve such problems.