BOSTON - Leaders on Beacon Hill are laying the groundwork for civilians to replace police officers on some roadside construction details, but critics are raising doubts about whether the move will lead to any substantial savings.

Gov. Deval L. Patrick and top legislators have agreed that the administration will write regulations for using civilians with flags to direct traffic at some less-traveled construction areas.

The administration would have 90 days to write the regulations, according to a bill on Patrick's desk. The intent is to consider using civilian flag people on secondary roads or dead-end streets, not major highways.

Police have long used the details to hike their salaries, sometimes into six figures. Police have defeated several attempts in the past to limit their detail work or supplant them with civilians.

David G. Tuerck, executive director of the Beacon Hill Institute at Suffolk University in Boston, said legislators and the governor may be too beholden to police unions to break the police grip on details at road construction or utility sites.

Under the provision, the regulations would not affect police details if they are guaranteed in municipal contracts or local ordinances or bylaws.

"That takes all the teeth out of it," said Tuerck, whose institute estimated that cities and towns would save between $37 million and $67 million each year by replacing police details with civilians.

Michael J. Widmer, president of the Massachusetts Taxpayers Foundation, said he's skeptical of any big savings from the regulations partly because many efforts for change have failed in the past.

"There's an opportunity for the administration to take a stand and do it in a way that is fair," Widmer said.

Widmer said the details are a key part of the agenda of police unions. "Everybody is leery about touching it," he said.

Police make campaign contributions to legislators and the governor and they also work for candidates during elections.

During the 2005 and 2006 election cycle, for example, the Boston Police Patrolmen's Association gave $40,000 to candidates and the Massachusetts Police Association gave $21,875.

While advocates said civilians would save money, police argue that they provide a level of public safety, visibility and clout at road construction sites that would be missing with civilian flaggers.

Richard Brown, president of the State Police Association of Massachusetts, said police are concerned about any changes that could be spurred by the bill.

State police earn $42 an hour on the details, while municipal police earn an average $38.50 an hour.

Brown and Raymond F. McGrath, lobbyist for the International Brotherhood of Police Officers, said they doubt officials will find any meaningful savings through the use of civilian flaggers.

They cited the state's prevailing wage law, which requires a "prevailing wage" for all workers on publicly-financed construction projects. The statewide average prevailing wage for a laborer such as a flagger would be $34 an hour, according to McGrath.

Add in health insurance, union dues and safety considerations and it would likely make little sense to hire a civilian for the work, they said.

"Who would you rather have?" McGrath asked. "An ineffective pole holder or a fully trained police officer with the skills and ability to make a difference at the site?"

Patrick's press secretary said the governor is looking for opportunities to cut costs.

"We stand ready to work with the House and the Senate to determine when it is safe and cost-effective to use flagmen on road-side projects," spokesman Kyle Sullivan stated.

Rep. Joseph F. Wagner, D-Chicopee, said civilian flaggers might eventually be used when the state awards contracts for work on municipal roads or bridges, as long as public safety is assured. Wagner said he hopes it leads to some savings.