Yarmouth is joining other school districts in Maine that are installing cameras on the stop arms of school buses to deter motorists from passing buses that are stopped to pick up or drop off children.

A new state law, enacted June 10, authorizes school districts to equip buses with external cameras that record the license plates of vehicles that unlawfully pass stopped buses. The law allows a $250 fine for a first offense and a 30-day license suspension for a second offense.

During the first eight school days this year, the Yarmouth School Department has recorded three instances of drivers passing a stopped bus with students in the area, Superintendent Andrew Dolloff told parents in a districtwide email Friday.

“Clearly, this is unacceptable, and it is a concern that I believe requires more attention throughout the entire region in order to prevent a tragedy from occurring here in Yarmouth or anyplace else,” Dolloff wrote. “I am hopeful that this letter, along with other efforts to publicize this concern, will make an impact on driver behavior in our region.”

Scarborough and Rockland-based Regional School Unit 13 are among the Maine school districts that have added external cameras.

Maine is among 19 states with similar laws, according to the trade magazine School Bus Fleet. Adam Mayo, transportation director for Topsham-based Maine School Administrative District 75 and president-elect of the Maine Association for Pupil Transportation, told the magazine that the new state law “opens the door” for school districts to use extended stop arms legally and enables bus drivers to concentrate on the safety of students without worrying about recording identifying information about offending vehicles.

Oklahoma and Tennessee are among the states to enact similar laws recently. Lawmakers in California and Florida are considering legislation. In New England, Connecticut, Massachusetts and Rhode Island also allow stop-arm cameras.

In a phone interview, Dolloff said the cameras are being installed as a deterrence. The district has not turned over images of offending vehicles to police yet, but Dolloff said the district would do so soon, and he hopes police follow up on the information the district provides and pursue fines.

“It takes awhile to process it. We have to fill out reports. There are no outcomes yet,” the superintendent said. “But from our perspective, we are going to push for that to happen.”

Messages left with Yarmouth Police Chief Daniel A. Gallant were not returned Friday night.

According to the state law, the footage from the mounted cameras is confidential and can only be released to law enforcement, prosecutors, a defendant or court when an infraction has occurred. Also, the footage can be retained for just 30 days unless it is part of an investigation.

The camera only records when the arm is extended and images show the license plate of the vehicle that is passing the bus, not the driver, Dolloff said. “It doesn’t tell you who the driver is, but we can tell you who the vehicle is registered to,” he said.

Each camera costs “a few hundred dollars,” Dolloff said. The Yarmouth School Department spent $6,600 outfitting its fleet of 15 buses with the cameras, he said.

“What is amazing is how frequently it is happening,” he said of stopped school buses being passed. “Our school committee was shocked when I told them there had been three instances in the first eight days of school. Most law-abiding citizens assume this is a rare occurrence – who doesn’t stop for a school stopped with its lights on? But it’s happening a lot.”

In his letter to parents, Dolloff quotes the district transportation supervisor, Bruce Bickford, as saying that drivers who pass buses “are running late, impatient or simply careless.”