It's hard to avoid the overpowering presence of billboard advertisements. This constant exposure, from driving in a car to walking on the streets, means that we become consumers even when we least expect it. However, many artists are working to subvert the power such ads have over us. Some have covered billboards in their own creations while others have converted the gigantic structures into art pieces. Check out the various ways artists have approached commercial spaces with 15 Ways Art Projects Have Taken Over Billboards.