Effects of Idle Time Restrictions on Excess Pollution from Construction Equipment

Construction vehicles and equipment contribute to air pollution. To reduce pollution, numerous state and local jurisdictions limit the amount of time diesel engine vehicles or equipment can run at idle without shutting down. These restrictions vary widely indicating a need for improved understanding of the relationships between pollutant emissions and regulations establishing a maximum idle time in a construction setting. Previous studies have found that a reduction in operational efficiency will increase the amount of excess pollution, that is, the amount of pollution created in excess of that emitted by a construction operation under ideal conditions. Shutting down an engine can create a delay in re-entering the work stream and, therefore, reduce operational efficiency. In another study, the authors found that excess pollution would be minimal with a reasonably well-balanced, minimum or near minimum cost, construction equipment fleet composed of a single wheel loader (WL) working with different numbers of off-road dump trucks (OTs) on an independent soil-moving operation. This paper describes the results of an investigation using computer-based simulation techniques to determine the excess pollutant emissions for the same equipment conducting the same earthmoving operation, including the effects of a number of typical restrictions on maximum allowable idle times. Equipment emissions were based on previously published field data.