Through-tunnel estimates of vehicle fleet emission factors

Peter Brimblecombe, Thomas Townsend, Chui Fong Lau, Agata Rakowska, Tat Leung Chan, Griša Močnik, Zhi Ning

Research output: Journal article publicationJournal articleAcademic researchpeer-review

37 Citations (Scopus)


On-road measurements of traffic-related gas and particle pollutant concentrations in three tunnels in Hong Kong and high resolution pollutant concentration profiles obtained while driving through the tunnels were used to derive the individual pollutant gradients using parametric and non-parametric (Sen-Thiel) slopes and compared with the commonly used entrance-exit two points calculation. The fuel based emission factors of measured pollutants for individual tunnels at different times of day were derived from gradients using a new method based on fuel carbon balance principle. Combined with the tunnel traffic volume and composition, the average tunnel emission factors were analyzed by linear regression to derive the diesel fleet emission factors. Average nitrogen oxides (NOx) and black carbon (BC) emission factor for diesel fleets are 29.3 ± 11.0 gNO2kg-1and 1.28 ± 0.76 g kg-1of fuel, respectively. The results from the study were compared with the emission data from vehicle chasing approaches and the literature, showing reasonable agreement. Practical limitations and future direction for improvement of our method were also discussed. The method presented in this study provides a convenient drive-through approach for fast determination of tunnel and individual vehicle fleet emission factors. It can be used as an effective and fast approach to validate the emission inventory and to evaluate the effectiveness of policy intervention on the traffic emissions.
Original languageEnglish
Pages (from-to)180-189
Number of pages10
JournalAtmospheric Environment
Publication statusPublished - 1 Dec 2015


  • Black carbon
  • Carbon monoxide
  • Emission factor
  • Hong Kong
  • Tunnel
  • Ultrafine particles

ASJC Scopus subject areas

  • General Environmental Science
  • Atmospheric Science


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