The Grand Tour has tried to answer that question. I thought the turnstiles idea was really good, especially if you place them in a building with heavy traffic.

The Grand Tour has tried to answer that question. I thought the turnstiles idea was really good, especially if you place them in a building with heavy traffic. Though probably not really cost effective. https://www.youtube.com/watch?v=WhwyH6tT-EQ https://www.youtube.com/watch?v=WhwyH6tT-EQ