Development of an enforcement strategy for low-emission heavy-duty vehicles in California

It is anticipated that tighter emission standards will require development of advanced electronically controlled HD engines, possibly with aftertreatment devices. However, there is a concern these new technologies may be susceptible to reliability and durability problems, and they may be subject to improper maintenance and tampering, all of which subsequently leads to deterioration and emission increases. The objective of this study was to evaluate the need for HDLEV enforcement and to propose effective enforcement strategies to ensure HDLEV in-use emission compliance. The electronically controlled HD engines with no aftertreatment devices were determined to have a lower failure rate compared to mechanical engines. However, if aftertreatment devices were used it would significantly increase the failure rate of those engines. The frequency of occurrence was determined to be higher for defects caused by improper maintenance and tampering than those caused by manufacturing error. The components estimated to have the highest frequency of failure were the aftertreatment devices, EUI, and electrical connections. The defects with the most significant impact on PM emissions were PM trap removal and defective EUI. The defects with the most significant impact on NOx emissions were EGR failure and advanced injection timing. The excess emissions caused by improper maintenance and tampering were higher than those generated by manufacturing defects. It was determined the most cost effective approach for targeting manufacturing errors would be using the chassis dynamometer test. However, this approach would require to set the in-use standards in g/mile and it would still require at least a doubling of the current budget for this program. Among enforcement approaches targeting improper maintenance and tampering, the approach using the concept of OBDIII was determined to have the highest effectiveness. The approach with the second highest effectiveness was the PSI program modified with the requirement of OBD system use for HDLEV and the mechanic's enhanced training. The HDVIP was determined to have the lowest effectiveness even after incorporating the OBD system and mechanic's training and licensing requirement.;This research has resulted in a better understanding of enforcement needs for HDLEV, which should assist ARB in formulating effective enforcement strategies in the future.