This study, prepared for Detroit Diesel Corporation, evaluates the emission impacts and cost-effectiveness of more stringent emissions standards for heavy heavy-duty diesel engines (HHDDEs) that will take effect 1 October 2002 under consent decrees entered into between the US Environmental Protection Agency and the manufacturers of these engines. The consent decrees require that the HHDDEs meet a 2.5 gram per brake-horsepower-hour standard for the sum of nitrogen oxide and non-methane hydrocarbon emissions beginning in October 2002. The 15-month acceleration of the standard, which would otherwise go into effect under EPA regulations in January 2004, is known as the “Pull-Ahead.” Current information indicates that the costs of implementing the standard will be higher and the lead-time for motor carrier fleets to test the new technology engines before October 2002 will be shorter than anticipated.

The study takes these factors into account in estimating the emission reduction benefits and the cost-effectiveness of the Pull-Ahead and concludes that the high costs of the new vehicle standard and its early implementation will have effects that reduce the net emissions benefits of the Pull-Ahead to approximately 36 to 43 percent of the expected amount. It also finds that the higher costs and reduced benefits together will cause the emissions benefits to cost almost 60 times as much as was anticipated.