On-road emission factors derived from measurements in a traffic tunnel

Abstract

On-road emission factors for CO, CO2, NOx, N2O, total hydrocarbons and 9 speciated hydrocarbons were measured in a traffic tunnel in Goteborg, Sweden, in winter 1994/95. Ten-minute resolution pollutant measurements were made by using both FTIR-spectroscopy and conventional analysers during a 3-week period, in parallel with measurements of windspeed, traffic flow and speed through the tunnel. In addition, 7 speciated hydrocarbons were measured as weekly averages by means of diffusive samplers during a six-month period. On-road emission factors typically increased by a factor of up to 10 during congestion compared to smooth driving conditions, clearly demonstrating the large impact of driving behaviour on emissions. Furthermore, it was found that on-road emission factors agreed with emission factors derived from chassis dynamometer measurements within on ±10-20% for CO and NOx, whereas for HC the on-road emission factor was 50% higher.