Montgomery officials approved a bill on Tuesday that would outfit some school buses with automated, external cameras to ticket drivers who fail to yield to schoolchildren getting on or off a school bus.

County officials say the bill — like laws allowing speed cameras and red-light cameras — will help police at a time when budgets are tight. The law makes Montgomery the third county in Maryland, behind Frederick and Calvert, to pass such legislation.

It remains unclear how many buses might be outfitted with the cameras, and how much the program will cost. Todd Watkins, director of transportation for Montgomery County public schools, said that the cameras can cost $5,000 to $8,000 each and that school officials hope to start with about two dozen buses next school year.

Montgomery has more than 1,200 school buses, and they transport up to two-thirds of the county’s 147,000 students to 200 public schools and to 50 private facilities for special-education students.

County police say drivers on both sides of the road are required to stop if there is no physical median when a school bus’s lights are flashing and its stop-arm is extended. Drivers on the same side as the bus must always stop. Most of the violations occur on medium-usage roads, such as Old Columbia Pike, according to school and police officials.

Police officers are able to ticket a violator they witness in the act, and that fine ranges from $570 to $1,000.

County Executive Isiah Leggett (D) must set the ticket amount for those caught on camera, and a spokesman says it hasn’t been determined when he will make that decision. The fine can go as high as $250, according to the bill, and no points will be assessed against the driver’s license. Revenue collected from the tickets will go to program costs, Watkins said.

Montgomery has had internal bus cameras since about 2006, according to officials for the school bus drivers’ union, Service Employees International Union Local 500. School officials have tested external cameras since 2009, monitoring vehicular movement to the left of the bus when its ignition is on. Those cameras, which are separate from the automated ticketing cameras, will be installed on all new buses.

Council member Valerie Ervin (D-Silver Spring) introduced the bill last November after the drivers’ union approached her.

Hours before the vote, county, schools and union officials held a news conference about the school bus bill. Dozens of attendees — among them reporters and school, county and union staff and reporters — stood near a parked school bus as Ervin and others extolled the potential benefits of the bill.

“It is a behavior that must be stopped, and anything we can do . . . is incredibly important,” Montgomery County Superintendent Joshua Starr said at the news conference.