Effects of road grade on real-world tailpipe emissions of regulated gaseous pollutants and volatile organic compounds for a Euro 5 motorcycle

Abstract Road grade is an important variable that affects engine power demand and hence the fuel consumption and tailpipe emissions of vehicles. However, no prior works have evaluated the effects of road grade on tailpipe volatile organic compound (VOC) emissions of motorcycles. This study investigated the effects of road grade on real-world tailpipe emissions of carbon monoxide (CO), carbon dioxide (CO2), total hydrocarbons (THC), nitric oxide (NO), and speciated VOCs for a Euro 5 motorcycle. Real-world emissions of CO, CO2, THC, and NO were measured in real-time using a miniature portable emissions measurement system (mini-PEMS), while VOCs were measured in integrated exhaust samples collected during real-world driving. PEMS tests (n = 20) were conducted on urban (UR), suburban (SU), uphill (UH), and downhill (DH) routes. The road grade range encountered in this study was approximately −14 % to +14 %. The mean UH emission factors of CO, THC, and ΣVOC were 9890 ± 1619, 101.0 ± 6.7, and 18.81 ± 4.31 mg/km, respectively. Likewise, the DH emission factors were 202 ± 197 mg/km for CO, 10.3 ± 2.9 mg/km for THC, and 1.49 ± 0.68 mg/km for ΣVOC. The emission factors of all measured pollutants on the UH route were significantly higher than the DH and baseline (mean of UR and SU) emission factors. The results of the present study may help identify emission hotspots along the roads and formulate traffic air pollution control strategies.