Diagram 1 shows changes in the cargo transport distance and its cost.

Diagram 1: Changes in Freight Movement between 1960 and 1998

From CRA D02378-00 Report

Although general public still has negative feeling toward diesel engine, the vast majority of the heavy-duty trucks that transport the freight fueling the US economy and contributing to daily life are diesel-powered.
Nevertheless, increased awareness of the importance of fuel economy brought about by energy policies and rising gasoline prices has led the federal government to establish fuel economy standards, called the Corporate Average Fuel Economy (CAFE), which stipulate minimum fuel economy levels for a manufacturer's fleet of passenger cars or light trucks with a gross vehicle weight rating (GVWR) of 8,500 lbs. (3856 kg) or less. At present, CAFE standards call for passenger cars to achieve a fuel economy of 27.5 mpg (11.6 km/L) and for light-duty trucks to achieve 20.7 mpg (8.7 km/L). Although these standards are in place until 2004, there is a strong possibility that even stricter regulations will be enacted beginning with the 2005 model year. New standards are now being studied by the US legislature, and there are even some lawmakers calling for an elimination of the present car and light-duty truck categories and a single standard of 35 mpg (14.8 km/L) for all vehicles. If in fact such stringent standards are adopted, there are many who feel that compliance with just gasoline-powered vehicles is likely to prove difficult, and that manufacturers will turn to diesel engines to improve fuel economy.
In the face of these trends, the onus is on manufacturers to eradicate the negative image held by many Americans of diesel engines by the timely application of cleaner emission technology and undertaking of information campaigns about clean diesel technology.