An Investigation of the Uncertainty of Handbook of Emission Factors for Road Transport (HBEFA) for Estimating Greenhouse Gas Emissions: A Case Study in Beijing

Abstract

The reliability of estimation of emissions under the Handbook of Emission Factors for Road Transport (HBEFA) model has not been thoroughly studied and the mechanics of the model have not been fully investigated. The HBEFA structure of typical driving cycles is analyzed in this study regarding its uncertainty for estimating greenhouse gas (GHG) emissions. The key parameter of the HBEFA model, relative positive acceleration (RPA), is analyzed for its sensitivity to GHG emissions. The results indicate that uncertainties in estimation of GHG emissions do exist in the HBEFA model. The uncertainties are derived from the adoption of selected driving cycles and from the parameter of RPA. Given the uncertainties of estimating the GHG emission factors of driving cycles, it might be difficult for the selected driving cycles to represent all traffic situations. Uncertainties also exist in the selection of the top-20 driving cycles. For the selected samples of driving cycles, the sensitivity of RPA is found to be insufficient in describing the emission differences, due to the insensitivity of RPA to acceleration and deceleration. Different driving characteristics may still yield the same RPA, which indicates the potential inability of RPA to capture specific traffic scenarios such as intersections, ramps, and congestion.