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To reduce noise transmission on a busy street, you have to break up sound waves. Generally, if a barrier blocks your view of the road, it will reduce the noise level.
Trees will work. Evergreens are better than hardwoods because they are fuller and stay that way all year long. Plant a screen of them as close to the roadway as possible.
A fence is another option. It should be solid, such as a stockade-type fence, to block the noise. Again, you want it as close to the noise source as possible.