Hose or wipe
Now you can either hose it off with strong water pressure, or wipe it away with a wet Dirty Deeds microfibre cloth. For extreme cases you might have to give it a second go, concentrating your efforts on the most heavily marked areas. On tar especially, you will be amazed to watch it slowly dissolve away. It can be quite dramatic on a white or light coloured car as marks you were not even sure were tar, tend to be removed as well.