Research Contracts

New Search

Project at a Glance

Title: Measuring real-world emissions from the on-road heavy-duty truck fleet

Principal Investigator / Author(s): Kirchstetter, Thomas

Contractor: UC Berkeley

Contract Number: 12-315

Research Program Area: Emissions Monitoring & Control

Topic Areas: Field Studies, Mobile Sources & Fuels, Modeling, Transport

Research Summary:

The Air Resources Board (ARB or Board) Truck and Bus Regulation is leading to the introduction of exhaust aftertreatment devices to reduce emission of particulate matter (PM) to 0.01 grams per brake horsepower-hour (g/bhp-hr) and oxides of nitrogen (NOX) to 0.2 g/bhp-hr. This would lead to the introduction of diesel particulate filters (DPF's) to control PM on a majority of California fleet by 2014 followed by gradual phase-in of model year (MY) 2010 engines, such that by 2023, all the heavy-duty diesel engines operating on California roadways will meet the MY 2010 heavy-duty engine standard. The PM and NOX emission reductions realized by the introduction of aftertreatment devices are far greater than those associated with normal fleet turnover. However, along with the emission reduction benefits, there may be some unintended consequences of using such devices such as concomitant increase in ultrafine particle numbers, ammonia (NH3) emissions and the nitrogen dioxide (NO2) to NOX emission ratio. It is therefore important to measure actual on-road emissions in order to quantify the overall effect of the regulation.

CARB-funded studies being conducted near the Port of Oakland are already demonstrating significant emission reductions occurring in the port truck fleet due to implementation of CARB's Drayage Truck Rule. The proposed research will build upon these and other sampling programs performed at the Caldecott tunnel by measuring emissions from the broader on-road truck fleet at three stages of implementation of CARB's statewide Truck and Bus Regulation: 1) 2014, when a significant fraction of the truck fleet will be equipped with DPF's; 2) 2015, when pre-1994 engines will be replaced with MY 2010 engines; and 3) 2017, when pre-1996 engines will be replaced with MY 2010 engines, and by which time a significant portion of the fleet will have MY 2010 engines or newer engines. The measurements will be performed at the Caldecott tunnel in the San Francisco bay area, where an uphill grade will ensure that the trucks operating under load have elevated exhaust temperatures to make aftertreatment systems functional (i.e., urea injection is active). The results of this study will be used to quantify emission factor distributions, identify unintended consequences, investigate the durability and failure rates associated with the introduction of aftertreatment, and establish emissions benefits resulting from the Truck and Bus Regulation. CARB staff may perform further analysis to assess compliance of on-road fleet with the provisions of the Truck and Bus rule.


For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 322-3893

Stay involved, sign up with CARB's Research Email Distribution List