|FHWA > Engineering > Pavement > Asphalt > Hot Mix Asphalt for
the Undergraduate| In the United States in 1988 there were
approximately 4 million miles of roads of which 2.3 million were
surfaced with asphalt or concrete. The balance of the roads were
surfaced with either gravel, stone, or soil (1.3 million miles),
or they were non-surfaced (0.4 million miles). Of the hard
surfaced roads, approximately 96 percent of the 2 trillion
annual vehicle miles of travel occurred on these hard surfaced
roads. In 1998, expenditures for highways were over $68 billion
at all levels of government. Since 1981, these expenditures have
grown at an annual rate of over $3.5 billion. The $68 billion
spent in 1988 included $32 billion for capital outlays and $20
billion on maintenance activities. During 1988, the amount of
HMA produced and placed in the U. S. was estimated to be 500
million tonnes valued at some $10.5 billion. The HMA industry
directly employs some 300,000 people and indirectly accounts for
an additional 600,000