The problem I found in NYC subway is that there are many abandoned metro cards. This is the small problem that people can see it everywhere. First of all, the metro cards are made with plastics and the cards are hard to be collected for recycling. The cards can only be used for limited time and people have to change a new one. Hopefully, in the future people won’t be using the cards to get into the station.

The solution I found is to let people stop using the cards, instead, people can download an app to their phone. There won’t be anything blocks the way into the station but a sensor that can collect money from the app and also check who didn’t pay.