Suggested Citation: Henderson, Dennis K., Brett E. Koenig, Patricia L. Mokhtarian (1994) Travel Diary-Based Emissions Analysis of Telecommuting for the Puget Sound Demonstration Project. Institute of Transportation Studies, University of California, Davis, Research Report UCD-ITS-RR-94-26
Transportation control measures are often implemented for their environmental benefits, but there is a need to quantify what benefits actually occur. Telecommuting has the potential to reduce the number of daily trips and miles traveled with personal vehicles and consequently, the overall emissions resulting from vehicle activity. This research, sponsored by the Washington State Energy Office (WSEO), studies the emissions impacts of telecommuting for the participants of the Puget Sound Telecommuting Demonstration Project. The California Air Resources Board's emissions models, EMFAC7F and BURDEN7F, are used to estimate the emissions on telecommuting days and non-telecommuting days based on travel diaries completed by program participants. This study, among the first of its kind, represents the most sophisticated application to date of emissions models to travel diary data. Analysis of the travel diary data and the emissions model output supports the hypothesis that telecommuting has beneficial transportation and air quality impacts. The most important results are that telecommuting decreases the number of daily trips (by 30%), the vehicle miles traveled (by 63%), and the number of cold starts (by 44%), especially those taking place in early morning. These reductions are shown to have a large effect on daily emissions with a 50 to 60% decrease in pollutants generated by a telecommuter's personal vehicle use on a telecommuting day.
Reductions of this magnitude are observed because the telecommuters in this sample are long-distance commuters, with commutes twice as long as the regional average. As telecommuting becomes more widely adopted, and the average commute length for telecommuters becomes more representative of the average, the per-capita impacts on travel and emissions reported here will decrease. Also, there are many factors that should be considered as part of a total assessment of the air quality impacts of telecommuting. These include an analysis of the direct transportation impacts (the only impacts addressed here), as well as the indirect transportation impacts, indirect non-transportation impacts, and region-specific topographical and meteorological factors. However, the net impacts are still expected to be beneficial—a reduction in VMT and emissions.