State police and more than 150 municipal departments will be watching for aggressive drivers during the fourth wave of Smooth Operator enforcement Sunday through Sept. 15.

PennDOT says Smooth Operator targets aggressive driving, which it says is the leading cause of highway fatalities in Pennsylvania. During last year's Labor Day weekend, 739 crashes and nine deaths resulted from aggressive behavior such as speeding, tailgating, running red lights and careless passing.

During a wave of enforcement last month, police issued 19,433 citations, including 15,567 for aggressive driving. The first year of the statewide program resulted in 59,567 citations and arrests. PennDOT has budgeted more than $2 million for police training, overtime and equipment such as wireless infrared speed detectors