The dual-track price system is the intermediate price system from the state control price system to the free market price system.
In China prior to 1978, most prices were set by the government alongside quantity targets. When the need for reform was accepted, there arose the question of how to move the economy from a planned one towards a market-oriented system. Chinese economic reformers took the view that the best way was to keep the existing planned economy, but gradually to build up a free market system alongside it. In 1981, the central government allowed some enterprises which had fulfilled their planned production quotas, to sell their surplus output at market prices, while their planned quota production was sold at state-set prices.
(China.org.cn September 16, 2009)