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Operational efficiency is a simple way of addressing nonproductive time of diesel-powered construction equipment that performs a construction activity and is defined as the ratio of nonidle activity time to total activity time including idle time. The effects of diesel equipment operational efficiency on total emissions for construction activities have not been fully established; thus a fundamental understanding of operational efficiency is needed to evaluate the effects on total pollutant emissions of diesel-powered construction equipment. This paper presents a methodology to assess the effects of equipment operational efficiency on the total pollutant emissions of construction equipment performing construction activities. This methodology estimates the percentage of additional pollutants emitted due to a reduced operational efficiency, based on the ratio of idle to nonidle emissions. Results for a case study of six bulldozers indicate that pollutant emissions, in addition to the minimum amount required to complete a specific quantity of work, increase as operational efficiency decreases. This conclusion allows the savings resulting from increased efficiency to be determined. Furthermore, additional pollutant emissions for a specified operational efficiency increase as the ratio of idle to nonidle emissions increases. The ratio of idle to nonidle emissions varies according to pollutant and is approximately 1:2 for hydrocarbons and carbon monoxide, 1:5 for nitrogen oxides, and 1:7 for particulate matter.

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