given the limitations on truck weight and size, increased productivity in the industry comes from two sources: fewer empty miles and less time waiting between loads. u.s. department of transportation figures indicate that empty routes have continued to account for 29% of single-unit truck traffic; this has been equated to an annualized 15 billion gallons of gasoline, $30 billion cost, or 149 million tons of excess carbon emissions. traditional freight brokers acted as intermediaries to manage the coordination of freight, helping independent drivers or companies match loads with available empty trucks. increasingly, computerized brokers are threatening the future of traditional human brokers by offering increased efficiency. in addition, shipper-driven brokerage over the internet enables shippers to post loads and solicit bids directly from carriers. instead of relying upon traditional freight brokers, shippers function as their own brokers, dealing directly with freight companies.