13. Type of Report and Period Covered

Supported by general revenues from the State of Texas. Air pollutant emissions and fuel consumption are the most important problems associated with vehicle idling. Truck idling in particular is more problematic than other vehicles mainly because of the duration of idling and the high amount of emissions produced. This report is intended to identify the characteristics of truck idling emissions by collecting data using an advanced portable emission measurement system (PEMS), in which the attempt is made to measure actual idling emissions from truck tailpipes and to relate measured emissions to altered pre-testing driving conditions. Employed for the testing is.the On-Board Emission Monitoring system OEM-2100TM, an advanced PEMS., This equipment can determine the second-by-second emissions of HC, CO, CO2, O2, and NOx in the exhaust gas by a functional equivalent of a repair-grade dual five-gas analyzer subsystem. Altered driving circumstances considered during truck idling tests include cold starts and hot starts, different distances and durations of driving before the tests, different roadway facility types used while driving, different durations of idling tests, etc. Measured emissions under all the different pre-testing driving conditions are then analyzed and compared. In addition, the measured idling emissions are compared with emissions estimated by the emission facto