A tri-oval is a shape which derives its name from the two other shapes it most resembles, a triangle

Triangle

A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....

 and an oval

Oval (geometry)

In technical drawing, an oval is a figure constructed from two pairs of arcs, with two different radii . The arcs are joined at a point, in which lines tangential to both joining arcs lie on the same line, thus making the joint smooth...

. Rather than meeting at sharp, definable angles as the sides of a triangle do, in a tri-oval these angles are instead rounded into smooth curves. While an oval has four turns, a tri-oval has an "extra" fifth turn. This term is most often used to describe the shape of many automobile racetracks, including:

• Daytona International Speedway
  Daytona International Speedway
  Daytona International Speedway is a race track in Daytona Beach, Florida, United States. Since opening in 1959, it has been the home of the Daytona 500, one of the most prestigious races in NASCAR. In addition to NASCAR, the track also hosts races of ARCA, AMA Superbike, Grand-Am and Motocross...
  
  
• Talladega Superspeedway
  Talladega Superspeedway
  Talladega Superspeedway is a motorsports complex located north of Talladega, Alabama, United States. It is located on the former Anniston Air Force Base just outside the small city of Lincoln. It was constructed by International Speedway Corporation, a business controlled by the France Family, in...
  
  
• Walt Disney World Speedway
  Walt Disney World Speedway
  Walt Disney World Speedway is a racing facility located on the grounds of the Walt Disney World resort near Orlando, Florida.It was built in 1995 by IMS Events, Inc., a subsidiary of the Indianapolis Motor Speedway Corporation, and was designed primarily as a venue for the Indy 200 at Walt Disney...
  
  
• Kansas Speedway
  Kansas Speedway
  Kansas Speedway is a tri-oval race track in Kansas City, Kansas. The speedway was built in 2001 and currently hosts two annual NASCAR race weekends. The IndyCar Series also raced at the speedway until 2011...
  
  
• Sanair Super Speedway
  Sanair Super Speedway
  Sanair Super Speedway is a .826 mile paved triangular oval race track. The facility also holds a quarter mile dragstrip. It is located in Saint-Pie, Quebec. It hosted the Molson Indy Montreal from 1984 to 1986...
  
  
• Nazareth Speedway
  Nazareth Speedway
  Nazareth Speedway was an auto racing track in Lehigh Valley, Pennsylvania which operated from 1910 to 2004. The track is often associated with local drivers Mario and Michael Andretti. It was associated with Frankie Schneider in its earlier dirt track history....
  
  
• Pikes Peak International Raceway
  Pikes Peak International Raceway
  Pikes Peak International Raceway, also known as PPIR, is a participant focused racetrack located in Fountain, Colorado, south of Colorado Springs and north of Pueblo...
  
  
• Pocono Raceway
  Pocono Raceway
  Pocono Raceway also known as the Tricky Triangle, is a superspeedway located in the Pocono Mountains of Pennsylvania at Long Pond...
  
  
• Calder Park Thunderdome

The use of the tri-oval shape for automobile racing was conceived by Bill France

Bill France

Bill France may refer to one of two people involved in NASCAR, father and son:*Bill France, Sr. , nicknamed "Big Bill", the founder of NASCAR and its president from 1948–1971...

 during the planning for Daytona

Daytona International Speedway

Daytona International Speedway is a race track in Daytona Beach, Florida, United States. Since opening in 1959, it has been the home of the Daytona 500, one of the most prestigious races in NASCAR. In addition to NASCAR, the track also hosts races of ARCA, AMA Superbike, Grand-Am and Motocross...

. 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

Indianapolis Motor Speedway

The Indianapolis Motor Speedway, located in Speedway, Indiana in the United States, is the home of the Indianapolis 500-Mile Race and the Brickyard 400....

) 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. It is recognizable in most tracks by a manicured grass area.