A New Approach to Estimate Vehicle Emissions Using Inductive Loop Detector Data

Abstract

Motor vehicles are significant contributors to urban air pollution and greenhouse gases. Common practice for estimating vehicle emissions in California calls for integrating travel forecasting models and emission models. However, static travel forecasting models are incapable of generating the detailed vehicle activity required for emission estimates. Further, the fleet mix is also assumed to be constant across different roadways and at all times of day. Therefore, this article attempts to develop a new approach to measure travel activity and vehicle mix using existing inductive loop detector data. However, this study does not intend to forecast future vehicle activity. The study found that current practices overestimate speeds as much as 5–25 mph, whereas the proposed method overestimates speed about 2 mph, compared to ground-truth speeds in a freeway corridor. Furthermore, contrary to current practice, the proposed model distinguishes the vehicle miles traveled (VMT) between light-duty vehicles and heavy-duty vehicles in each link. The current practice overestimates or underestimates emissions by 1–20% during different times of day, whereas the proposed method underestimates the emissions by about 3%. We conclude that the proposed approach can provide a cost-effective way of estimating reliable emission inventory and estimating time-dependent emission inventories for different pollutants.

Keywords:

• Emissions
• Inductive Loop Detector
• MOVES
• Vehicle Classification
• Vehicle Reidentification

Acknowledgments

This work was performed as part of the California Partners for Advanced Transit and Highways program of the University of California. It also was partially supported by the University of California Transportation Center program. The contents of this article reflect the views of the authors, who are responsible for the facts and accuracy of the data presented. The contents do not necessarily reflect the official views or policies of the state of California. This article does not constitute a standard, specification, or regulation. The authors also gratefully acknowledge the cooperation and assistance of Fred Yazdan of the California Department of Transportation and John Slonaker of Caltrans Division of Research.