Tri-oval

More formally, according to the four-vertex theorem, every smooth simple closed curve has at least four vertices, points where its curvature reaches a local minimum or maximum.

The triangular layout allowed fans in the grandstands an angular perspective of the cars coming towards and moving away from their vantage point.

Traditional ovals (such as Indianapolis) offered only limited linear views of the course, and required fans to look back and forth much like a tennis match.

The tri-oval shape prevents fans from having to "lean" to see oncoming cars, and creates more forward sight lines.

In other racing vernacular, the term "tri-oval" is also used to specifically describe the part of the track which represents the top triangular point of the course, which is used as the main stretch, the pit straight and usually the start–finish line.