Navistar International has dropped its lawsuit against the Environmental Protection Agency after the EPA agreed to hold a public workshop or hearing to address Navistar's concerns regarding the agency's certification policies for selective catalytic reduction-equipped diesel trucks.

Last year, Navistar, which is alone among engine builders with its preference for advanced exhaust gas recirculation over SCR as an emissions reduction technology, asked a federal court to review EPA's decision-making to allow use of SCR to achieve 2010 emission standards. The engine company alleged that EPA violated federal procedures, circumventing the normal rulemaking process, when it changed its mind about allowing SCR.

Back in 2001, when EPA issued the final rule outlining the 2007 and 2010 emission regulations, the agency was looking at NOx adsorbers to comply with the NOx emission standard. Urea SCR technology was not considered feasible by the EPA, for reasons including the establishment of a urea distribution infrastructure and concerns about engines running without the solution in the urea tank.

Since then, the agency has decided that SCR can be a solution, and the technology has already gone into effect. In March 2007, the agency issued a guidance document on emission certification of engines equipped with urea-SCR technology.

Navistar had asked the U.S. Court of Appeals in Washington, D.C., to void those polices because they had been adopted by the EPA without the proper rulemaking procedure. In its appeal, Navistar claimed the EPA was using those policies to allow SCR-equipped diesel powered trucks to operate for extended periods without any control of NOx emissions and is certifying SCR engines as meeting NOx emission requirements when they do not.

Under the deal reached Monday, EPA has agreed to "engage in a public process to reexamine its policies, for future 2011 and later model year engines," during which it will "provide a thorough review of EPA's policies regarding operation of SCR-equipped engines." In addition, the agency said it will "ensure, among other things, that SCR equipped heavy-duty diesel engines are designed to properly control emissions as required under applicable regulations."

The agreement must be published by EPA in the Federal Register for comment before it can become final.

"We believe that with full and open public participation, EPA will develop a new approach that will result in equal enforcement of the 2010 NOx requirements for all engine makers," said Jack Allen, president of Navistar's North American Truck Group.