Engine Tests Demonstrate Feasibility of LNT on Heavy-Duty Diesel Engine: To comply with future exhaust emissions regulations, most heavy-duty diesel vehicles will be equipped with an aftertreatment device based on urea selective catalytic reduction (SCR) to reduce NOx at the tailpipe. Another aftertreatment such as a lean-NOx trap (LNT) has only been applied to light-duty diesel vehicles. Because of the relatively low conversion rate and durability problems, LNT has not been considered for heavy-duty vehicles. Researchers at New Advanced Combustion Engineering previously developed the super-clean diesel engine (SCDE) for heavy-duty vehicles to demonstrate the feasibility of reducing both fuel consumption and exhaust emissions with a high exhaust gas recirculation (EGR) rate (e.g., more than 60 percent) and high intake charge pressure (e.g., as high as 400 kPa). NOx was reduced below 1.0 g/kWh. Subsequently, researchers questioned whether applying a LNT to SCDE would be feasible to reduce tailpipe NOx under JE05 test conditions and tested a SCDE equipped with a LNT to investigate the performance of the LNT in reducing tailpipe NOx. Although researchers did not address the issue of durability, they presented somewhat promising results as far as the NOx reduction capability of the LNT. The chapter reports the demonstration results of the LNT on a heavy-duty diesel engine. The chapter consists of 9 pages including 8 figures and 2 tables.