Carbon Monoxide Categorical Hot-Spot Finding Tool

This site was created to help project sponsors determine if their project parameters fall within the acceptable range of modeled parameters to rely on the CO categorical hot-spot finding. FHWA modeled a large intersection (described below) to determine the resulting maximum CO concentrations for the project. Project sponsors may be able to rely on the CO categorical hot-spot finding in place of doing their own CO hot-spot analysis as part of a project level conformity determination in CO maintenance areas if the project's parameters fall within the acceptable range of the finding's modeled parameters. Reliance on the CO categorical hot-spot finding is still subject to existing interagency consultation and the public involvement requirements under NEPA and the conformity rule (40 CFR 93.105) for the individual project.

FHWA's CO Categorical Hot-Spot Memo and Finding can be found on the main FHWA CO Categorical Hot-Spot page includes a full discussion regarding use of the CO categorical hot-spot finding. Further supporting material (FHWA's CO Categorical Hot-Spot Finding Technical Document and model inputs/outputs) can also be found at the same location. Note: This finding only applies in urban areas and in States other than California.

Summary of urban intersection analyzed:

Urban Intersection - Go to Project Form >>

Signalized intersection
Perpendicular approach angles
4 through lanes and 2 left turn lanes per approach and 4 departure lanes per each leg of the intersection
12-foot lanes
10-foot receptor offset distance from the edge of pavement
No median
±2% grade on one cross street and 0% grade on the other cross street
LOS E
Peak hour traffic volumes of 2640 vehicles per hour on each approach
Peak hour average speeds of 25 mph on each approach
Average intersection control delay of 78.5 seconds per vehicle during the peak hour
5% heavy-duty trucks

Minimum requirements:

Ambient temperature in the project area of -10 degrees Fahrenheit or greater
Analysis year 2017 or later
1-hour background CO concentration in project area less than or equal to 32.6 ppm
8-hour background CO concentration in project area less than or equal to 7.3 ppm
Meteorological persistence factor of 0.7 or less