So Cal Rebel is correct.
Many of our track guys drive to the track on Hoosier R6's. They are DOT approved, steel belted radials and street legal.
I wouldn't care to drive on them in the rain or in very cold temps, but we don't get much of that here.
PS2's for the street, R6's or Kumho V710s for the track.
Not a fan of the Cups as they don't work as well on the street as the PS2's and don't work as well at the track as R6's.
The VRL Hoosiers you see above are good track tires, they're just too thin to drive on the street. They will pick up nails, screws, etc. and may leave you stranded. If you trailer your car, you can get VRL's from Archer Racing.
Dan