Weird looking spots on the freeway?

What the heck are those red and black marks on the freeway (35 Southbound) near the new parking ramp around the Lakeville or Burnsville area in MN? It looks like a red or black spot probably a 1-2 feet around that looks like something was dragged along the road. The color fades as it gets further away. There is usually one black one and one red one. They come and go. I haven't noticed one recently but used to see them all the time?? Weird?