In the U.S., approximately 24 million children ride school buses everyday, spending an average of an hour and a half each weekday in a bus.

Because children are particularly at risk to many environmental exposures, the EPA is urging school districts in the United States to take measures to make school buses more environmentally friendly. In particular, there are concerns about exhaust emissions and other fumes associated with school bus operations.

The EPA is recommending that school districts attempt to eliminate unnecessary school bus idling, retrofit buses that remain in fleets with better emission control technologies or buses that use cleaner fuels, and replace the oldest buses in the fleet with less polluting buses.

Idling is identified to be a significant problem that can lead to environmental problems and also make children sick. Unnecessary school bus idling pollutes the air, wastes fuel and causes extra engine wear.

Idling buses can pollute the air in and around the buses. Exhausts from buses that idle may enter school buildings through air intakes and open windows. Diesel bus exhaust from excess idling can cause a health concern, especially for children who are lined up waiting to board the buses.

Idling buses also wastes fuel and money. Typical school bus engines burn about a half a gallon of fuel per hour of idling. School districts that eliminate idling can save significant money..

In addition, school bus engines do not need to idle for more than a few minutes to warm up. There are myths suggesting that more is required, but in point of fact less idling is better.

In fact, extended idling can actually cause engine damage. Engine manufacturers often recommend that there be no more than three to five minutes of idling.

One manufacturer, Caterpillar, Inc., cautions drivers to avoid excessive idling. If a vehicle is parked more than five minutes it is recommended that the engine be turned off.

Other procedures recommended by the EPA include:

• Assigning cleanest buses and fleets to the longest routes.

• Inform drivers that following other buses too closely may contribute to higher concentrations of exhaust inside the bus. Drivers are encouraged not to caravan.

• Arrange bus departure times so that buses do not queue for lengthy periods.

• Encourage children to sit in the front of the bus if the bus is not full.

• Examine the layout of the loading areas for schools, reconfiguring to reduce queuing and idling.

Finally, it is recommended that parents be advised to turn off their cars when they wait to pick up and drop off children. Schools should also prohibit delivery trucks from idling on grounds.