The driver, a 48-year-old man from Centereach, was heading westbound on Veterans Memorial Highway near New Highway between 9:30 a.m. and 10 a.m. when his truck went into the ditch, police said.
Pieces of fencing had been falling off the flatbed truck before the driver crashed, and a police spokeswoman said several calls reporting fence and debris in the roadway came in at about 9 a.m.
The driver was taken to St. Catherine of Siena Medical Center in Smithtown. Police did not have immediate information on his medical condition but said he was otherwise not hurt in the crash.
No other injuries were reported.