Assessing the influence of boundary conditions, driving behavior and data analysis methods on real driving CO2 and NOx emissions

Roberto A Varella; Marta V Faria; Pablo Mendoza-Villafuerte; Patrícia C Baptista; Luis Sousa; Gonçalo O Duarte

doi:10.1016/j.scitotenv.2018.12.053

Assessing the influence of boundary conditions, driving behavior and data analysis methods on real driving CO₂ and NO_x emissions

Sci Total Environ. 2019 Mar 25:658:879-894. doi: 10.1016/j.scitotenv.2018.12.053. Epub 2018 Dec 11.

Authors

Roberto A Varella¹, Marta V Faria², Pablo Mendoza-Villafuerte³, Patrícia C Baptista⁴, Luis Sousa², Gonçalo O Duarte⁵

Affiliations

¹ LAETA, IDMEC, - Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, - 1049-001 Lisboa, Portugal. Electronic address: roberto.varella@tecnico.ulisboa.pt.
² LAETA, IDMEC, - Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, - 1049-001 Lisboa, Portugal.
³ CHN Industrial, - Via Puglia 35, - 10156 Turin, Italy.
⁴ IN+, Center for Innovation, Technology and Policy Research, - Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, - 1049-001 Lisboa, Portugal.
⁵ IN+, Center for Innovation, Technology and Policy Research, - Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, - 1049-001 Lisboa, Portugal; ADEM, Mechanical Engineering Department, - Instituto Superior de Engenharia de Lisboa (ISEL), Rua Conselheiro Emídio Navarro, 1, - 1959-007 Lisboa, Portugal.

PMID: 30583183
DOI: 10.1016/j.scitotenv.2018.12.053

Abstract

The need to verify vehicle emissions in real world operation led to the implementation of Real Driving Emissions (RDE) test procedures, effective since September 2017 for new Euro 6 cars following the Commission Regulation (EU) 2016/427, which defines the RDE test conditions and data analysis methods to allow representative results. Main factors addressed by the regulation include the share of driving operation, ambient temperature range, altitude and elevation difference. However, RDE is still debatable since not only boundary conditions but also the evaluation methods and trip selection are being discussed together with a carbon dioxide (CO₂) regulation, which is planned to be implemented in the short term. Thus, this work focuses on analyzing the effect of different data measurement and analysis methods (i.e. cold-operation, road grade, trip selection and driving style) on CO₂ and nitrogen oxides (NO_x) emissions based on 13 RDE tests performed in the Lisbon Metropolitan Area, Portugal. The tests were conducted by 2 drivers using 5 vehicles. Each driver performed 2 trips per vehicle, one in normal driving and other in aggressive driving. A Portable Emissions Measurement System (PEMS) was used to collect 1 Hz data, which was compared and analyzed using the European Commission (EC) proposed method for RDE tests. Results show the effects of each parameter such as average difference between drivers (7% in CO₂ and 55% in NO_x emissions) and between aggressive and normal driving. For road grade, big oscillations happen during the slope profile, which impacts emissions during all trips. Considering cold-operation, CO₂ and NO_x emissions are, on average, ~25% and 55% higher, respectively, than in hot-operation. These results highlight the need for deeper studies on these factors to assure that RDE tests evolve to a more established certification procedure than laboratorial certifications.

Keywords: Data analysis methods; Fuel use and emissions; Portable emission measurement systems; Real driving emissions; Testing boundary conditions.