Impact of Engine Idling on Fuel Use and CO2 Emissions of Nonroad Diesel Construction Equipment

It is difficult to quantitatively assess the impact of engine idling on fuel use and emissions of construction equipment because of a lack of sufficient data. This paper presents a methodology for evaluating the impact of idling on fuel use and carbon dioxide (CO2) emissions of diesel construction equipment. The results are based on field data collected from 34 items of equipment. Engine idle time may be quantified in terms of equipment operational efficiency (eta), which is defined as the ratio of nonidle time to total equipment use time (nonidle time plus idle time). Using eta and the ratio of idle to nonidle fuel use and CO2 emission rates (r), the percentage increase in the total quantities of fuel used and CO2 emitted (N-E) were calculated for each item of equipment for values of eta less than the maximum theoretical operational efficiency of 100%. Results showed that as eta decreased (or idle time increased), N-E increased. A mathematical model that uses eta as a predictor variable was developed to estimate values of N-E. This model accounted for approximately 85% (R-2=0.85) of the variability in the data. Recommendations include using the model as a managerial performance measurement tool to assess idle restriction regulations and operational strategies of construction equipment. DOI: 10.10611(ASCE)ME.1943-5479.0000068. (C) 2012 American Society of Civil Engineers.