Research Projects

Project at a Glance

Project Status: complete

Title: Heavy duty truck population, activity and usage patterns.

Principal Investigator / Author(s): Fischer, Michael

Contractor: Jack Faucett Associates

Contract Number: 93-306

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


Heavy-Duty trucks (HDTs), both gasoline- and diesel-powered, are estimated to be among the largest contributors to the State of California's oxides of nitrogen (NOx) and particulate emissions inventory. The state implementation plan (SIP) for ozone contains a number of measures designed to control emissions from HDTs. However, HDTs are also one of the most poorly characterized categories of the emissions inventory. The objective of this study was to update historic (1960 to present) population distributions, develop a methodology for forecasting HDT populations (by weight class, fuel type, and age); characterize HDT activity levels (mileage accrual rates, VMT and cumulative mileage); and gather new data on important activity parameters (speed profiles, number of trips per day, average speeds and activity by time of day). Population and activity data were developed primarily by using Department of Motor Vehicles (DMV) registration data and historic data from the Truck Inventory and Use Survey (TIUS) conducted by the U.S. Bureau of the Census. It was estimated that in 1995 there were 661,287 HDTs registered in the state (59% gasoline and 41% diesel) that accounted for over 9.3 billion vehicle miles per year of driving. Out-of-State vehicles accounted for another 3.03 billion vehicle miles per year, or 24.6% of total statewide HDT VMT. While these data represent a major improvement over the data included in the current emissions models, a major conclusion of this study is that all users of HDT data in the state should work together to improve the available DMV data for analysis of historic HDT populations. Substantial new information about HDT activity was developed by instrumenting a small fleet (42 HDTs total) with onboard dataloggers. The analysis of the data indicated that the "average" HDT in the sample made 16.8 trips per day and 17.9 starts per day (starts include trips plus key-on to key-off events with trip length equal to zero mile) and that average speed was 30.6 mph. On average, trucks in the sample fleet spent 28.4% of their driving time at idle. The data also show some significant variations in activity based on weight class and usage (i.e., local vs. long haul driving). The activity data collected will be used to improve the ARB's emissions models, while some of the datalogger data from this study will be used to develop driving cycles in terms of speed versus time for HDT emission testing.


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

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