A proposed state regulation that would limit the idling of diesel-powered long-haul trucks, buses and delivery vehicles to five minutes an hour was endorsed by three local environmental groups and 846 people who signed a petition submitted at a public hearing in Pittsburgh on Friday.

The petition was presented at the Environmental Quality Board hearing by Ashleigh Deemer, program organizer at Clean Water Action, who cited the health and environmental benefits of reducing emissions of soot and nitrogen oxides and carbon dioxide from diesel engines.

Ms. Deemer said a recent study by the Clean Air Task Force shows diesel emissions contribute to approximately 162 premature deaths, 230 heart attacks, 2,306 asthma attacks and more than 13,500 missed workdays a year in Allegheny County.

Rachel Filippini, executive director of the Group Against Smog and Pollution, an Allegheny County environmental group, spoke in support of the proposal but suggested it be tightened to ban idling of school buses on school property to protect children who are more sensitive to air pollution.

Heather Sage, outreach director for Citizens for Pennsylvania's Future, a statewide environmental group, said the regulation should allow municipalities to adopt tougher idling rules to address local problems.

The Chicago-based Engine Manufacturers Association "generally supports efforts to eliminate unnecessary idling," according to Timothy French, an attorney for the diesel engine industry trade group, but he urged the state to adopt a rule consistent with the California Air Resources anti-idling rule.

Bill McMaster, account manager at the Kenworth Truck dealership in New Stanton, warned of ambiguities in the proposal and a lack of suitable equipment to implement it.

"I'm concerned that we could be forcing changes on the trucking industry when we don't have the infrastructure in place to operate under the new regulation properly," Mr. McMaster said.

At least 14 states, many of those surrounding Pennsylvania, already have diesel idling limit laws.

The hearing in Pittsburgh was the last of three on the idling rule held by the board this week.

Other hearings were in Harrisburg and Allentown. If approved by the board, the regulation would go to the Independent Regulatory Review Commission, with final action by that panel expected this summer.

The board will continue to accept public comments through March 17. Written comments can be addressed to Environmental Quality Board, Box 8477, Harrisburg, PA 17105-8477, or via express mail to the Rachel Carson Office Building, 16th Floor, 400 Market St., Harrisburg, PA 17101-2301.