Go to an auto parts store and purchase a can of aerosol brake cleaner. Spray it on the tar and dab it up with a terry cloth towel as it softens and comes loose. This product smells a little so air out the room after use.
I was extremely lucky when I read somewhere that Krud Kutter would take care of tar stains (and I happened to have a spray bottle of it). It is made to remove paint, oil, grease and tar! I couldn't believe how fast and easy it was! I have removed so many different types of stains from my carpet and linoleum, and it does not bleach or fade the area! Amazing stuff!