California Air Resources Board

Principal Investigator/Author: Kent Johnson

Contractor: University of California, Riverside

Contract Number: 14-302

Project Status: Completed

Relevant CARB Programs: Mobile Source Emissions Inventory, Mobile Source Emissions Research Program, Greenhouse Gas Emission Inventory

Topic Areas: Climate Change, Air Pollution, Heavy-Duty Vehicles, Heavy-Duty Vehicle Research

Research Abstract:

The objective of this research is to collect tractor-trailer activity data that will be used by CARB staff to assess the potential greenhouse gas (GHG) emissions benefit from improved trailer aerodynamics. Four different trailer types (flatbed, tanker, curtainside, and container chassis) that are not currently required to meet aerodynamic equipment requirements of CARB's existing Tractor-Trailer GHG regulation were targeted for evaluation. The study included an analysis of a national trailer registration database for the years 2000 through 2015, with 11,575 trailers for California that included 3,172 flatbed, 6,402 container chassis, 1,897 tankers, and 103 curtainside trailers. Fleet surveys were obtained from 51 fleets representing 17,032 trailers that provided information about fleet sizes, annual miles traveled, and load types. A limited number of fleets utilizing the four trailer types were data logged to better understand their activity patterns. Based on this limited dataset, there was no clear association between trailer type and the different operating characteristics of the fleets. Distributions of vehicle miles traveled (VMT) by speed for the different fleets showed similar trends, with the majority of the VMT occurring at highway speeds between 50 and 65 mph, when aerodynamic devices provide the greatest benefit.

Keywords: tractor trailer, activity data, greenhouse gas (GHG), emissions, vehicle miles traveled (VMT), fleet

Final Report: Please email research@arb.ca.gov to request the Final Report generated by this research contract.