Robberies and aggravated assaults on Metrorail and Metrobus were down last year after a spike in those serious crimes in 2010, according to a five-year report released by Metro Transit Police on Wednesday.

In 2011, the number of serious crimes that were reported dropped to 1,898, from 2,270. Robberies were down nearly 14 percent, to 871. Aggravated assaults fell to 108, from 136, and larcenies decreased to 791, from 925.

Metro Transit Police Chief Michael Taborn said the increase in thefts for 2009 and 2010 was attributable in part to a national trend that showed an “uptick in the stealing of electronics, iPhones and iPads.”

He compared it to previous trends in which thieves stole people’s gold chains or sneakers.

“When a trend happens and something becomes popular, the bad guys figure out they can take phones and electronics and get $200 to $300 per phone,” Taborn said.

The department of 450 officers has enlisted several tactics to curb electronic snatchings, Taborn said. Plainclothes officers have conducted stings at rail stations. The transit authority also plays more announcements in rail stations and posts signs warning riders that the items are at risk of theft.

According to police data, most of the serious crime in 2011 occurred on Metrorail; there were 1,177 crimes reported compared with 519 incidents in parking lots and 87 on Metrobuses.

Assaults on bus drivers, which had increased concern among workers worried about their safety, were also down. Police said there were 66 reported bus operator assaults in 2011 compared with 90 in 2010. Taborn said that’s due in part to increased patrols on Metrobus routes — mainly along the U Street corridor and east of the Anacostia River — that have reported problems.

Crime in parking lots fell to 641 incidents in 2011 compared with 848 the year before. Taborn said increased patrols at stations that have reported more problems, including Suitland and Greenbelt, have helped. Metro has also provided other police departments with SmarTrip cards so they can help randomly check parking lots, he said. The transit authority has also mailed postcards to drivers who leave change, CDs, Global Positioning System devices or other gadgets in view, warning them to hide the items.

Police made 1,922 arrests in 2011, fewer than the 2,008 made the year before. Taborn said the number of arrests is down because he has dispatched more police officers, including 20 from an anti-terrorism unit, throughout the system. Metro also plans to hire 50 more officers.

“If we’re more visible, we discourage people from committing crimes,” he said.