Carbon Monoxide and Nitrogen Oxides RelationshipsMeasured Inside a Roadway Tunnel and a Comparisonwith the Mobile 6.2 Emission Model Predictions

摘要

This paper presents the results of a multi-year carbon monoxide (CO) and nitrogen oxides(NOx) monitoring program performed inside the 8,000 foot long Ted William Tunnel (TWT),which is part of the Central Artery/Tunnel (CA/T) Project in Boston, Massachusetts.The monitoring program was performed in support of developing the CA/T Project’sOperating Certification for its tunnel ventilation system. The objective was to measure tunneloperating levels for both pollutants, and to develop a statistical method using monitored COlevels as a predictor for estimating NOx levels for compliance demonstration with theMassachusetts State’s 1-hour NO2 Policy Guideline. The program measured in-tunnel COand NOx levels on quarterly basis during 1997-1998 at the newly constructed TWT whenonly commercial traffic was permitted inside the TWT. The program was repeated during2004 when the tunnel was open to general traffic use. An analysis of the measured levels andthe derived relationship between the two pollutants based on more than 20,000 hours ofcollected data is described in this paper.The CO-NOx data proved that there is a good correlation between the two pollutants and thatNOx levels can be predicted as a function of CO levels within the TWT. The comparison tothe EPA MOBILE 6.2 Emission Factor Model predictions using all available project specificdata indicated that the CO/NOx ratios matched very well for the summer seasons, but thelarge increases in CO winter emissions predicted by MOBILE 6.2 did not occur during thethree years of data collection.