BELFAST, Me.  On America’s highways, wind turbines may be the ultimate oversize load.

Trucks carrying silvery blades nearly half a football field long have been lumbering through this placid coastal town all summer, backing up traffic as they slowly exit the roadway. Huge, tubular chunks of tower also pass through. Tall pieces of machinery looking somewhat like jet engines travel at night because they require special routing to avoid overpasses.

As demand for clean energy grows, towns around the country are finding their traffic patterns roiled as convoys carrying disassembled towers that will reach more than 250 feet in height, as well as motors, blades and other parts roll through. Escorted by patrol cars and gawked at by pedestrians, the equipment must often travel hundreds of miles from ports or factories to the remote, windy destinations where the turbines are erected. In Belfast, officials have worked hard to keep the nuisance to a minimum, but about 200 trucks are passing through this year on their way to western Maine, carrying parts that have been shipped from Denmark and Vietnam.

Plenty can go wrong despite months of planning. In Idaho and Texas, trucks laden with tall turbine parts have slammed into interstate overpasses, requiring hundreds of thousands of dollars in repairs. In Minnesota last year, a truck carrying a tubular tower section got stuck at a railroad crossing; an approaching train stopped just in time. Also in Minnesota, a woman was killed last September when her car, driven by her husband, collided at an intersection with a truck carrying a wind turbine. (After a police investigation, local officials found that the truck driver was not at fault.)

Maine had a glitch of its own two years ago, after a truck carrying a big piece of turbine got stuck for hours while trying to round a corner near Searsport, a port near Belfast that receives many turbine parts from overseas.