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FHWA and EPA National Near-Road Study Las Vegas

8 Summary

This report provides a summary of a field study conducted in Las Vegas, NV from Mid-December, 2008 thru Mid-December, 2009. The objective of this research study has been to determine MSAT concentrations and variations in concentrations as a function of distance from the highway and to establish relationships between MSAT concentrations as related to highway traffic flows including traffic count, vehicle types and speeds, and meteorological conditions such as wind speed and wind direction. Preliminary results include the following:

• Concentration gradients are observed for gaseous pollutants associated with distance from roadway, however more analysis is required.
• Higher pollutant concentrations are observed with higher traffic volumes.
• Effect of wind speed appears to be a factor with regards to concentration gradient (e.g., dilution effect) and needs to be investigated further.
• Non I-15 sources may be larger contributors than previously expected, for example:
  • Impact of near-by parking lot may be a factor at Site 2 and Site 3.
  • Las Vegas Boulevard (Site 3).
  • Airport and other potential sources.

Preliminary results of this study provide indications that highway vehicle emissions impact near-road air quality. Known highway vehicle pollutants such as CO, NO, NO₂ and NO_X have elevated concentrations in a near-road environment and decrease as one moves away from the road. Additional analysis of the data is needed to more accurately assess the effect of wind speed as well as other near-road effects.