Crossing the fog line twice, even in a wide truck, is enough reasonably suspicion to justify pulling it over.
United States v. Diaz, 2015 BL 289363, 2d Cir., No. 14-2505, 9/8/15
The Second Circuit Court of Appeals overturned the district judge's suppression order even though they agreed that many things could reasonably be the cause for a driver's failure to stay in the lane perfectly. The court stated that "a momentary but reasonable loss of attention because of the appearance of an insect in the cab, or a sudden loud sound or flash of light" could cause a momentary crossing over the fog line.
The court concluded, however, that the test is not whether the driver was actually careless or violated a traffic law, but whether an objectively reasonable police officer could have formed a reasonable suspicion that a violation occurred. Here, the court said, the officer's suspicion that a violation had occurred was reasonable because the truck crossed the fog line twice.
http://www2.bloomberglaw.com/public/desktop/document/United_States_v_Diaz_No_142505_2015_BL_289363_2d_Cir_Sept_08_2015
