The center was recently closed to traffic on a child basis making it much safer for pedestrians.
I'm struggling to understand exact meaning of this sentence. There are a lot of meaning in 'close' and 'traffic' so I don't know what to select as meaning.
In this context, traffic means cars, buses, motorcycles and possibly bicycles.
If an area is closed to traffic, it means that these types of vehicle are not allowed to pass through.
Note that the word child is probably a typo or mis-heard word: it should probably be trial.
