Effects of international roughness index on vehicle emissions

Abstract

Pavement conditions, such as roughness, measured by the international roughness index (IRI) play an essential role in improving vehicle fuel economy and GHG emission reduction. Considering this, the objective of this study was to investigate the relationship between IRI and vehicle emissions, derived from the HDM-4 model. IRI and speed values were collected for every 100 m for two road segments located in Brazil, State of Ceare, using a smartphone app called SmartIRI. The IRI values were inserted in the HDM-4 model, as well as the vehicle and road characteristics, in order to derive Instantaneous Fuel Consumption (IFC) and tailpipe emissions (TPE) for CO2, NOx, CO, SO2, HC and PM. The correlations between IRI and speed reached 99.8%. Regarding the relationship between IFC and the tailpipe emissions (TPE), ~49% and 63-64% of the HC and CO tailpipe emissions could be explained by fuel consumption and IRI variations, respectively.