How many nasscar tracks run two races during the season?

Sixteen NASCAR tracks hold at least two races during the season. They are the Bristol Motor Speedway, Charlotte Motor Speedway, Chicagoland Speedway, Daytona International Speedway, Dover International Speedway, Iowa Speedway, Kansas Speedway, Kentucky Speedway, Martinsville Speedway, Michigan International Speedway, New Hampshire Motor Speedway, Phoenix International Raceway, Pocono Raceway, Richmond International Raceway, Talladega Superspeedway and Texas Motor Speedway.