Prince William County’s overall crime rate fell to a 16-year low in 2010, despite a slight uptick in aggravated assault and larceny cases, according to the 2010 crime statistics report released Wednesday.

Last year, Prince William’s crime rate dropped from 19.5 crimes per 1,000 residents to 19.2, the report states. Violent crimes, including murder, rape and robbery, dropped almost 6 percent while aggravated assault and larceny went up 3.7 percent and 2 percent, respectively.

“Crime continues to be down significantly, and that’s a trend we’re seeing across the country,” Prince William Police Chief Charlie T. Deane said. “I think our strong neighborhood watch program and citizen’s police academy” have helped keep crime rates low.

The number of reported rapes dropped 7 percent in 2010, after almost doubling the year before, the report states. In all 53 rape cases reported, the victims were related to or acquainted with the offender, according to the report.

Crimes against property, which make up the majority of crimes in the community, rose 0.6 percent because of the increase in larceny cases, Deane said. The number of burglary and car theft cases both declined, Deane said, adding that he attributes the decline in car thefts to the increased use of vehicle security devices.

The report also breaks down the number of undocumented immigrants arrested in Prince William.

In 2008, county supervisors adopted a policy that requires police to ask the immigration status of people arrested on suspicion of violating state or local laws. Of the 1,785 people arrested last year in connection with major crimes, 138- or about 8 percent - were illegal immigrants, the report shows, noting that 80 percent of those arrests were for property crimes.

When looking at other offenses, about 20 percent of those arrested for public drunkenness were suspected illegal immigrants and about 16 percent of those arrested for drunk driving were suspected illegal immigrants, the report shows.

In addition to major crimes, the report addresses traffic offenses. The number of traffic accidents declined almost 7 percent last year, though the number of fatal accidents increased slightly, the report shows. In 2010, 22 people died from traffic accidents, including six pedestrians.