WALPOLE, Mass. — School bus contractor Michael J. Connolly and Sons will implement idling-reduction measures and pay a penalty of $33,000 to settle U.S. EPA allegations that it violated vehicle idling limits.

The Walpole-based company operates 300 school buses and provides student transportation services in 15 Massachusetts communities.

Under the settlement, Connolly will implement a suite of idling-reduction measures, including training all drivers, posting anti-idling signs, performing periodic “walk-throughs” of school bus lots to ensure that no excessive idling occurs, and notifying all school districts of the company’s policy against excessive idling.

EPA officials said that the company has responded quickly and has already implemented a number of the idling-reduction measures. Also, Connolly has a new fleet and a standard practice of replacing old buses with new buses every three years. Further, the company has committed to physically disconnect the “override” capability of the automatic shutoff mechanism on each school bus in its fleet, so that the automatic shutoff mechanism operates without interruption.

In December 2013 and January 2014, the EPA reportedly observed Connolly school buses idling for extended periods of time in company bus lots in the Massachusetts communities of Mansfield, Sharon, Walpole and Natick.

The EPA alleged that the company’s excessive idling was in violation of federally enforceable motor vehicle idling limits contained in the Massachusetts air quality state implementation plan. The regulations establish requirements for all motor vehicles operating in the state and, with very few exceptions, limit idling to no more than five minutes.

“Diesel exhaust is a serious health concern for children, both here in Massachusetts and across the country,” said Curt Spalding, regional administrator of the EPA’s New England office. “Reducing idling helps protect children’s health. Taking easy and common-sense steps to avoid excessive idling helps to save fuel and money, and reduces unnecessary air pollution.”

The Connolly settlement is the latest in a series of EPA enforcement actions designed to minimize excessive idling among school buses in New England. Since 2009, EPA New England has brought actions against six school bus operators, which agency officials said has led to substantial reductions in idling and emissions.