Why do Highways Need Noise Barriers?

In this video, we are defining why highways need noise barriers. The average noise level in a city neighborhood is about 40 decibels at night and 50 decibels during the day. There are a lot of different ways that highways cause noise pollution. Roads connect everyone to the rest of civilization. Since noise is a problem, it seems like the best way to protect the citizens is to put up Noise barriers.