Combined road courses combine the high speed characteristics of ovals with the technical precision of road courses. It allows road racing disciplines the unique experience of being held in the stadium style atmosphere of an oval superspeedway. Numerous combined road courses saw widespread use with sports cars in the 1970s and early 1980s. However, their use has since diminished considerably, since most layouts lacked the desirable topography and competitive challenges of natural road courses. In addition, most combined road course circuits offer poor sightlines for fans sitting in the grandstands. Oftentimes the challenging infield portion is obscured or not visible at all from the grandstands that line the circumference of the oval track, so many fans choose to view from the ground level inside the infield - leaving the grandstands mostly empty and unsightly.