How are truck sales doing worldwide? That depends on what section of the world you're talking about. Sales in the heavy-trucks segment of the U.S. market in the third quarter were up 29% compared to the same period a year ago, spurred on by a 39% September growth due to the tightening of the exhaust emission regulations.Despite that favorable stimulus, overall sales of medium and heavy trucks fells to 243,000 vehicles in the first nine months -- an 11% decrease over the first three quarters of 2001. September sales of medium trucks fell by 20%.In Germany, the production of light trucks up to 6 tons reached 19,000 units, a 13% decline from a year ago, and there was a 4% decline in trucks above 6 tons.In China, the commercial vehicle industry prospered as truck sales in the first eight months topped 1.39 million units, topping the same period in 2001 by 29%. Sales of heavy comercial vehicles above 16 tons have more than doubled, and they now account for 24% of overall truck sales.