Months after the MBTA instituted random bag searches on the T, it will install surveillance cameras on 155 buses with routes in Mattapan, Dorchester and Roxbury, said company spokeswoman Lydia Rivera.

Rivera said the surveillance cameras have long been on the MBTA’s agenda and noted that a recent increase in crime on buses has fueled the change, but installation will not be completed until the end of July.

Approximately five cameras will be installed on each bus to help ensure a safe drive along bus routes, she said.

“[The MBTA aims] to promote and maintain public transportation to citizens as an alternative to the car,” Rivera said. “With that said, we need to not only provide a system that is cost-efficient, reliable, but safe.

“It’s just one additional alternative to promoting safety for our customers,” she continued, “to more or less allow our customers to feel safe on the system.”

The cameras, which will be in clear sight and aimed at riders, will not record bus operators or other MBTA employees, Rivera said.

Rivera said the installation of the cameras should help deter individuals from harming themselves, other passengers or MBTA employees. The presence of cameras will also dissuade riders from vandalizing or tampering with bus equipment, she said.

On March 30, Dwayne Graham, an 18-year-old Hyde Park resident, was shot and killed in broad daylight aboard a bus at Washington Street and Columbia Road in Dorchester, according to an April 7 Boston Herald article. According to the article, there have been 288 “part-one” crimes – which include murder, robbery, rape, assault and larceny – between January 1 and March 31 on public transportation vehicles in Boston. The article states violent acts on or around public transportation are 15 percent higher during the first three months of 2007 than at the same time period last year.

Though some oppose the increased security measures because of privacy concerns, Eric Bourassa, a consumer advocate for the Massachusetts Public Interest Research Group, said cameras will prove to be a good addition to public transportation if their presence helps foster a sense of security among passengers.

“There are issues around improving public safety, so that crime doesn’t happen and people feel safe,” he said. “[But] you have to balance that with people’s sense of privacy – that ‘big brother’ is watching [feeling].”

Bourassa said the MBTA’s decision to install cameras is similar to the effective installation of cameras at intersections in Europe, where photographs are taken of cars that run red lights, allowing police to easily issue tickets through the mail.

Steve MacDougall, president of the Boston Carmen’s Union, the MBTA transit professionals union, said statistics show that crimes committed against passengers and mass transportation employees decrease when cameras are installed on buses. In addition, fare evasion is also reduced when buses are equipped with cameras, MacDougall said.

“I think it offers another layer of added deterrent for anyone who would commit a crime, at least on the buses,” he said.