Unnecessarily Impeding Normal Traffic Flow
It seems counterintuitive that driving too slowly may be unlawful, especially whereas stories of tragic accidents much more commonly involve incidents caused by excessive speed; however, similar to driving at an excessive rate of speed, driving unnecessarily slowly can also be dangerous.
While defensive driving is always encouraged, driving unnecessarily slowly, and thereby becoming an unexpected obstacle to other traffic, or possibly frustrating other drivers so significiantly as to cause others to act erratically, can pose significant danger.
Driving too slowly may be an offence contrary to the Highway Traffic Act, R.S.O. 1990, c. H.8 which states:
132 (1) No motor vehicle shall be driven on a highway at such a slow rate of speed as to impede or block the normal and reasonable movement of traffic thereon except when the slow rate of speed is necessary for safe operation having regard to all the circumstances.