In the 1970s Zambia had one of the best highway networks in sub-Saharan Africa. In 1991 it was estimated by the National Road Fund Agency (NRFA) that 80 percent of the road network had deteriorated and out of total road assets valued at US$2.3 billion, US$400 million had been lost due to neglected maintenance. The government introduced a road fund levy on fuel and that together with international aid has improved the highway network. In 2004 the NRFA rated 57% of paved roads in good condition, 22% in fair condition and 21% in poor condition.