Thefts on the Chicago Transit Authority, a category that includes the snatches of smartphones, tablets and other electronic devices from transit riders, increased 16 percent in the first nine months of the year compared with the same period in 2011, according to Chicago police data.

Robberies on the CTA declined from January through September of this year compared with the first nine months of 2011. Robberies, which involve force or intimidation, increased by 69 percent from 2009 through 2011, a Chicago Tribune analysis done this year found.

On Friday, Chicago police reported a 20 percent drop in batteries on the CTA system and a 3 percent decline in assaults from January through September of this year compared with that period in 2011. A Tribune analysis using the crime data portal showed a 5 percent decrease in batteries but a 4 percent decline in assaults, slightly better than the department's official figure.

Authorities attributed much of the success in reducing robberies to expanded video surveillance at rail stations and on trains and buses, in addition to other crime-fighting strategies, says the Tribune report. Future plans include programming real-time camera feeds on trains and buses to help authorities catch thieves and robbers in the act of committing crimes or immediately afterward, officials said.

Some 135 arrests, mostly for thefts and robberies, were made on or near CTA property from January through September, the report said.