Analysis of Motor Vehicle Emissions in a Houston Tunnel during the Texas Air Quality Study 2000

Measurements collected in a Houston tunnel were used to develop CO, NOx, and Non-Methane Organic Compound (NMOC) emission factors for on-road gasoline vehicles. The Houston NOx emission factor was at the lower range of emission factors reported in previous (primarily pre-1996) tunnel studies while the Houston NMOC emission factor was slightly higher than the emission factors reported in the previous tunnel studies. Comparison of individual hydrocarbon concentration ratios based on the tunnel data to ratios based on data obtained by aircraft flying at low levels over major transportation corridors showed relatively higher ratios of most hydrocarbon concentrations to MTBE and acetylene in the ambient environment than in the tunnel.