Fewer drivers in Montgomery County are illegally passing school buses that have stopped to let children on and off, but the number of violations continues to trouble administrators and elected officials as the school year is about to start.

A new Maryland survey shows that on a single day in April, school bus drivers witnessed 3,392 vehicles passing stopped buses on roads across the state, ignoring the buses’ stop arms and flashing lights. The violations reflect a decline of more than 50 percent since a similar day-long survey in 2011.

Montgomery, Maryland’s largest school system, accounted for nearly a third of state lawbreakers in the 2013 survey, with 1,078 drivers failing to halt for a school bus that was picking up or dropping off students.

“To have that many potential tragedies is mind-boggling to me,” said Todd Watkins, director of transportation for Montgomery schools. “Especially for a one-day figure, I think that’s very high.”

The survey measured illegal activity by collecting one day of reports from bus operators across Maryland’s 24 school systems. Nearly 5,000 bus drivers participated.

By law, drivers may not pass a school bus when its stop arm swings out and lights flash on, unless the cars are on the opposite side of a divided highway, police said. The law is designed to protect children as they approach buses and as they walk away after exiting.

Public education campaigns, news media attention and law enforcement efforts could be helping to reduce violations, officials said.

“The threat of getting a hefty fine never hurts,” said Bill Reinhard, spokesman for the State Department of Education, which sponsored the survey. “There’s been improvement, but we still have a ways to go.”

No recent Maryland fatalities have been linked to illegal passing of school buses, Reinhard said. Still, he said, “every violation is a potential fatality. Children, especially young children, are at risk when they leave a bus.”

Montgomery saw a nearly 28 percent decline in reported violations from 2012 to 2013, according to the survey. The school system transports about 100,000 of its 150,000 students by bus, with routes to more than 200 schools.

Video cameras are already installed on about 300 of Montgomery’s 1,267 school buses, and violators caught on video now receive warning letters from police.

The Montgomery County Council approved a measure last year to outfit some buses with new external law enforcement cameras — similar to red-light and speeding cameras — that would automatically issue citations to drivers who illegally pass a school bus that is picking up or dropping off children.

But the project has moved slowly as county attorneys explore legal questions involving the contract, said council member Valerie Ervin (D-Eastern County), the lead sponsor of the legislation.

“We just hope that we don’t have a child who is injured or harmed,” said Ervin, who voiced concern about the number of violations counted in the state survey. “That’s extraordinary to me. We have to do something about this. This is a very serious problem.”

There were fewer violations spotted in Prince George’s County — drivers noticed 599 in a single day — but the numbers there showed an uptick from the previous year, when there were 417.

In Montgomery, two or three students boarding or exiting buses have been injured by passing motorists in the past seven or eight years, said Watkins, the transportation director.

The state survey figures come as Prince George’s schools prepare to open Monday. Montgomery schools are scheduled to begin classes Aug.26.

Large school systems, with more buses and routes, reported the most violations, state officials said. Baltimore County reported a drop of more than 50 percent, and Frederick County reported a decline from 238 violations last year to 24 in April.

Three small counties — Kent, Somerset and Talbot — did not report any violations on the day of the survey.

State officials say that if motorists are caught by camera, fines of up to $250 may be imposed. Direct police involvement in a violation could mean up to $570 in fines and two to three points on a driver’s license.