University of Washington Study: School Bus In-Cabin Emissions
Scientific research conducted over the past several years has evaluated whether diesel particulate matter (PM) emissions are a significant contributor in air quality inside school buses. Peer-reviewed studies of tests using a tracer to assure accurate evaluations prove that vehicle tailpipe emissions are not a significant source of PM on the bus. Studies focusing on vehicle crankcase emissions are now being undertaken with reliable evaluation methodology. This Fact Sheet provides preliminary information on the crankcase emissions research under way at the University of Washington, with the support of International Truck and Engine Corporation.
Study Confirms — Tailpipe Exhaust Not Contributing to Emissions in Bus Cabin
* Preliminary findings of an ongoing study being conducted at the University of Washington, directed by Dr. Sally Liu, confirm that diesel tailpipe exhaust adds virtually no diesel particulates to the in-cabin air of school buses operating under normal conditions.
Reliable Technique Used to Measure Crankcase Emissions
* Using a reliable, precise evaluation technique and taking advantage of a favorable, very low ambient or background PM conditions in the test area (Seattle, WA), University of Washington conducted accurate measurement of particulate contribution from the school bus crankcase.
Key Finding: Crankcase PM Very Low, Less than Levels from Roadway Emissions
* The crankcase contribution to PM inside the bus was determined to be below the amount from background PM along the roadway. This very low PM finding indicates a less severe relative in-cabin air impact than has been found in other crankcase emission studies in other locations using a less-reliable research method.
* Preliminary study results indicate that the very low crankcase contribution to PM inside the bus can be reduced to near-zero levels with crankcase emission controls.
Common Sense Operations Help Reduce In-Cabin Emission Levels
* Operational factors, such as reduced idling and no prolonged opening of the doors during idling, have been identified as useful in maintaining in-cabin air quality.
More Study Underway
* Additional study already underway includes advanced diesel technology school buses that achieve the near-zero emissions levels from all sources (both tailpipe and crankcase) that is mandated for all new diesel school buses beginning in 2007.
* The additional research also examines the impact of technology control options (such as retrofits) on in-cabin air quality.
* International Truck and Engine Corporation is contributing support to this ongoing research, and will make information public as it is released by the University of Washington.
