Several of the nation’s largest trucking companies may cut back or eliminate their usual purchases of next year’s Class 8 tractors due to concerns over new-generation engines, reports Transport Topics. The new, cleaner-burning engines are scheduled to hit the market in the 2003-model year. However, some manufacturers claim they are behind in developing such engines, which emit 40 percent less nitrogen oxide, and some fleet managers fear the new engines may be less reliable than their predecessors.