Platform screen doors

Okay kiddo, you know how when you are waiting for the train, there is a big gap between the platform and the train? Well, sometimes it can be dangerous because people can fall in the gap or get too close to the moving train.

So, some train stations have something called "platform screen doors" which are like big walls that go all around the edge of the platform, almost like a fence.

These doors are usually made of glass or thick plastic and they have special sensors that can tell when a train is coming. When the train is near, the doors slide open to let people get on and off the train, and when the train leaves, the doors slide closed again so that nobody can get too close to the track.

This way, people can stay safe and there's less chance of accidents happening. Pretty cool, right?