WASHINGTON — An effort by federal regulators to mandate certification of crane operators has been languishing for almost four years.

A proposal to implement such a requirement is likely to be included in safety recommendations the agency expects to make public this year, a Labor Department spokeswoman said yesterday. Creating the new rule is a "top priority," said spokeswoman Sharon Worthy.

There have been three fatal crane accidents in recent weeks, including a collapse in New York yesterday that killed two construction workers and seriously injured another. Experts say such collapses are typically caused by wind or operator error.

The Occupational Safety and Health Administration's existing rules for workers who operate cranes have not been updated since 1971, though the agency acknowledges modernized standards could help prevent future accidents. Meantime, more than a dozen states have operator licensing requirements.

OSHA has been working with the industry on updated rules since 2003 and they reached consensus on a range of issues in July 2004, including the crane operator certification requirement.

The Labor Department in May estimated there are as many as 82 fatalities annually associated with cranes in construction "and a more up-to-date standard would help prevent them."

Troy Barringer, owner of ABC Crane Co. in Rockwell City, Iowa, said a federal mandate would be good for the industry since some companies use unqualified personnel to operate the equipment.

"When you don't know what you're doing, bad things can happen," Barringer said.

States with licensing requirements for crane operators, such as Connecticut, Massachusetts and New York, had among the lowest workplace fatality rates in 2006, according to the American Society of Safety Engineers.

In an effort to explain why four years have elapsed since the federal crane certification rules were first agreed upon, Worthy said the implementation process is very complex, requiring her agency to prove that the rules won't place undue burden on industry, among other things.

David Heidorn, manager of government affairs and policy at the American Society of Safety Engineers, criticized the government delay and said the negotiated rule-making process with industry should have helped get the rule in place more quickly. However, he acknowledged that OSHA's standards development process is underfunded while facing constant, intense scrutiny.

The two main causes for crane collapses are excess wind and operator error, said Steven Murray, an engineer at consulting company Exponent Inc. in Menlo Park, Calif., who has investigated more than five accidents and has never seen a collapse caused by a manufacturing defect.

Problems can arise when trying to lift the crane up as the building grows, a process known as "jumping" that reportedly led to separate fatal crane accidents in March in New York and Miami. An unstable load that is too heavy or too far away from the crane's base can also lead to a collapse, said Murray.

Having three, high-profile crane accidents in such a short time period is "extraordinary," said Graham Brent, executive director of the National Commission for the Certification of Crane Operators in Fairfax, Va.