A recent lawsuit filed by the Boston Police Patrolmen’s Association, seeking to prevent the city from forcing officers to wear body cameras for a pilot program, is not the first time the city’s police unions have apparently tried to stall policy changes adopted by some other US cities.

Police departments across the country, responding to citizen demands for greater transparency and accountability, have adopted such measures as mediation, creation of independent civilian review boards, and, more recently, use of body cameras.

Although the Boston Police Department has long been celebrated for its dedication to and achievements in community policing, Boston has traditionally been slow to adopt such innovative policing measures — although it has eventually done so in some cases.

Take for instance the department’s new mediation program, which was launched last fall and is designed to reduce a backlog of complaints against police officers by quickly resolving minor grievances.

Disagreements with the unions and questions about costs and logistics delayed the start of the program for a decade.

And despite a police-commissioned report by Northeastern University’s Institute on Race and Justice in 2005 outlining the type of police oversight board Boston should have, Mayor Thomas M. Menino settled for a civilian board that is powerless and far too dependent on the Police Department.

Menino pointed to union opposition and concerns about excessive oversight of the police as reasons for establishing the limited board two years later.

Analysts point to the evolving role of public safety unions in cities such as Boston, New York, and Philadelphia. In those cities, unions have had more of an impact on department policy, at times making it difficult to make even the simplest changes.

“The role of the unions has gone beyond the traditional goal of working conditions, but into an area that is a management prerogative,’’ said Chuck Wexler, executive director of the Police Executive Research Forum, a Washington-based think tank.

“The challenge is in some cities [the unions] look at every change in management policy as a chance to negotiate,’’ Wexler said. “The unions have really stepped into an area that makes it challenging for management.’’

The Rev. Jeffrey Brown, a cofounder of the Boston TenPoint Coalition, which provides services to at-risk youth, puts it more directly: “The police unions have played the power-behind-the-throne role. Their mandate to protect their officers at all costs’’ has impeded meaningful progress.

Former Boston police commissioner Ed Davis, who served as the city’s highest ranking police official from 2006 to 2013, compared his old job to that of a three-legged stool.

During his tenure, Davis pushed to install GPS tracking devices in police cruisers and to place cameras in district booking stations that would record officers booking suspects. The latter took several years of union negotiations to implement.

“You need support of the union, the mayor, and the community; if you lose any two, you can’t continue to function,’’ said Davis. “The community has this perspective that a police chief has an enormous amount of power in running the police department in a federally unionized state and it’s just not true. It requires enormous amounts of cooperation.’’

Mayor Martin J. Walsh, a former union leader himself, said that at times he has been frustrated over how difficult it can be to get certain things done, but he understands the purpose of the unions.

“The police unions have a responsibility to represent their members, and I think there are times — like with body cameras — that there’s such a big unknown out there. What does it actually mean to have them? What the ramifications are on how it works?’’ Walsh said. “This is all new technology and it’s all a change in the way officers do their job.’’

Boston Police Commissioner William B. Evans tapped a police consultant to select 100 officers at five police districts and from the Youth Violence Strike Force to participate in the six-month body camera pilot program after no officers volunteered.

The patrolmen’s association reached an agreement with the city for a volunteer program in July after negotiating for eight months.

In its lawsuit, the union alleged that the city violated collective bargaining agreements when it forced officers to participate.

The city is currently in contract negotiations with its police unions.

Evans was not available for comment.

During a recent interview on Boston Public Radio, Evans said he expected a fight from the unions over body cameras after announcing plans to force officers to wear them.

“That’s what the union does . . . they look out for their members,’’ he said in the interview. “An issue like this is something that — they want to make sure they protect their membership.’’

Officials representing the city’s three police unions did not respond to requests for comment.

While some say the lawsuit against the city over the body camera program is yet another example of an obstructionist tactic by the union, labor analysts say police unions play a significant role in protecting officers’ rights and safety.

“When management is making decisions by itself without the input of labor, they sometimes miss things that people in the trenches that people who have been in the head office might not be aware of,’’ said John Becker, an attorney with the Sandulli Grace law firm, who is representing the patrolmen’s association in its battle with the city over body cameras.

Police unions in Boston started to form shortly before the 1919 police strike, in which the city’s officers protested being underpaid and overworked.

By 1965, the Boston Police Patrolmen’s Association was established and, with 1,500 members, was making one of the most powerful public safety unions in the city.

The sheer numbers of the police unions’ membership also help boost their political clout.

“Mayoral candidates, gubernatorial and City Council [candidates] like to have a stamp of approval from police unions,’’ said Daniel DiSalvo, a senior fellow at the Manhattan Institute and an associate political science professor in the Colin Powell School at the City College of New York-CUNY.

Since 2001, the patrolmen’s association donated $440,683 to candidates running for state and city offices.

The Boston Police Detectives Benevolent Society and the Boston Police Superior Officers Federation donated $22,928 and $30,800, respectively, since 2002.

Spending on legal battles, according to the patrolmen’s association’s last available financial statement, totaled more than $800,000 to two law firms during a tax year that ended in August 2014.

Meanwhile civic leaders and fiscal watchdogs say the city should clamp down on police overtime spending and costly arbitration awards.

“I believe we are overspending in police overtime year after year,’’ said former longtime city councilor Charles Yancey, who has found himself at odds with the unions over legislation he sponsored to form an independent civilian review board and launch a body camera program.

“It’s the strength of the union that makes it difficult for the administration to get them under control,’’ Yancey said.

Jan Ransom can be reached at jan.ransom@globe.com. Follow her on Twitter at @Jan_Ransom.