Reduce traffic? How about stop building highly dense cities?
If you look at the figures published annually by the Texas Transportation Institute that are used to document congestion for each of the nation's major metro areas, you'll find that the cities with the worst congestion are those where a very large portion of the workforce is commuting to places OUTSIDE the central core. This is why Los Angeles, Washington D.C., Seattle and Atlanta always show up at the top of the list, and New York City -- which historically has had a bad reputation when it comes to traffic -- ranks somewhere down in the 70s.