Heavy-duty diesel vehicle use is expanding everywhere. In the U.S., California Air Resources Board (CARB) estimates that between 1990 and 2010, the number of trucks will increase by 70% and vehicle miles traveled will increase by 60% (CARB, 1998). In developing countries, the demand for freight movement and hence trucks will grow faster than gross domestic product and population (World Bank, 1996). The highest growth rates are predicted for Central and Eastern Europe, where trucking activity is expected to triple by 2015 (World Bank, 1996).