Metro trains have been involved in a troubling series of low-speed collisions in rail yards in the past four months as train operators have broken rules on speed and safe-driving practices, according to Metro’s safety oversight agency.

Metro has reported five or six rail yard crashes since December to the Tri-State Oversight Committee, which found that the incidents were due largely to lax compliance with rules, according to the committee’s chairman, Matt Bassett.

“Our concern comes from the fact that there is a pattern,” Bassett said. No one was seriously injured in any of the incidents, Bassett said, but some of them caused “a fair amount” of damage. He said the exact amount of the damage was being determined by Metro.

“We are addressing rail yard rules compliance to help ensure best safety practices, including conducting regular compliance checks in partnership with the TOC,” said Metro spokeswoman Lisa Farbstein.

The oversight committee recommended that Metro strengthen its enforcement of rail yard speed and driving restrictions. It will also begin carrying out inspections starting this week, Bassett said.

A 15-page TOC report, scheduled to be presented Thursday to a Metro Board of Directors safety committee, raises “concerns over rule compliance in rail yards” in an assessment of Metro safety since its last report in December.

Mortimer Downey, chairman of the safety committee, said in a statement that the TOC report “is a reminder of the importance of staying focused and remaining diligent about safety.” He said the board would be discussing the problems with observing rail yard rules.

The incidents are of particular concern in light of a November 2009 crash and derailment at the West Falls Church rail yard, when a six-car train struck a parked train, derailing two cars and injuring three workers. That accident caused $12 million in damage to the cars and left three beyond repair, Bassett said. The National Transportation Safety Board is investigating that crash and has not issued a final report.

“The memory of that incident informs our concern about this string of low-speed collisions,” Bassett said.

In the recent incidents, train operators were traveling at less than 15 mph but were not reducing their speed in segments of the yards, such as turns, that require slower travel, Bassett said. They were also not stopping at regular intervals to look around as required by Metro rules. That, in turn, led to crashes in which trains ran into other trains or into shop doors at the end of rail yards.

“It’s like pulling into your driveway and running into the garage door,” Bassett said.

Bassett said he was encouraged, however, by Metro’s recent efforts to reinforce the rules.

“We are pleased with the response they have put in place so far,” he said.

In its assessment, the oversight committee said Metro has made positive progress, particularly in “exemplary” work carrying out safety recommendations and investigations,and in training Metro employees on new rail-safety rules.

“While we have made great strides in catching up on a very large backlog of corrective action plans and accident investigations, there is still a good deal of work ahead,” Downey said.