A short track is an oval track less than one mile (1.6 km) long, with the majority being 0.5 miles (0.8 km) or shorter. Drivers seeking careers in oval track racing generally serve their apprenticeship on short tracks before moving up to series which compete on larger tracks. Due to their short length and fast action, these tracks are often nicknamed "bullrings". Professional-level NASCAR races on short tracks usually use a 500-lap or 400-lap distance. Short tracks in many cases have lights installed and routinely host night races. The short ovals still form the backbone of NASCAR in the feeder series. Three race tracks of this type are also represented in the Cup: Bristol, Martinsville and Richmond. At the request of some fans on social media, there are plans to hold more races on this oval type in the future. Tracks with potential for future cup races are the Iowa Speedway built in 2006, the Nashville Fairgrounds Speedway used until 1984 in the Cup, and the Memphis Motorsports Park, which had races of the Busch Series back then until the 2000s.