Freeways and Arterials. Based on the MOVES and CAL3QHC inputs described above, the EPA recommended persistence factor of 0.7, and the 8-hour background concentration of 2.6 ppm, Table 4.6 shows the one- hour modeled concentration lane and grade combinations for arterials and freeways in urban and rural locations that, under these conditions, cannot produce concentrations that could result in violation of the 8-hour CO standard. In all cases, the 8-hour CO standard, as opposed to the 1-hour standard, is the limiting case. Thus, freeway and arterial projects whose lane and grade conditions are less than or equal to those shown in Table 4.7 will not require a project- specific modeling to demonstrate compliance with CO ambient standards.
4.7.1.1 Sensitivity analysis for 11-foot wide urban freeway lanes
Freeways and Arterials. Table B-1, attached, shows the conditions for urban and rural arterials and freeways that would meet the one- and eight-hour NAAQS and would be covered by this PA34. The table shows one- hour concentrations, not including background concentrations. The populated cells of the table correspond to the lane and grade combinations for arterials and freeways which, even under worst-case conditions, would not result in exceedances of the 8-hour NAAQS for CO. Where the table entries are blank, the corresponding configuration would not meet the NAAQS based on 34These findings apply to scenarios with average speed ranging from 45 to 56 mph for arterials and 19 to 74 mph for freeways. worst-case modeling and would not be covered by this PA. Project-specific modeling would typically need to be conducted to show compliance with the NAAQS in these cases. For example, for a transportation improvement project for a freeway for which the build scenario has 10 total lanes, average road grades of 2% or less, and peak hour (congested) operating speeds of 50 mph, Table B-1 shows a contribution of 8.0 ppm for the one-hour CO standard. Since a CO concentration is shown in the table for this project type and configuration, the project is covered by this PA and does not require project-specific modeling for CO. Conversely, the same freeway with 12-lanes would not be covered by this PA, as the table entry is blank for that configuration. The values shown in Table B-1 were determined using conservative or worst-case modeling inputs and assumptions for MOVES and CAL3QHC (see Technical Approach discussion, below). Concentrations for comparison to the eight-hour NAAQS were determined from the one-hour values shown using a national average eight-hour background concentration of 2.6 ppm along with the EPA recommended persistence factor of 0.7. The resulting eight-hour concentrations were used to identify which arterial and freeway configurations would meet the eight-hour NAAQS. Note: this PA covers lanes widths of 11 feet or more for freeway and arterial project types.
Freeways and Arterials. Table A-1, attached, shows the conditions for urban and rural arterials and freeways that would meet the one- and eight-hour NAAQS and would be covered by the screening procedures presented here11. The table shows one-hour concentrations, not including background concentrations, based on national-level conservative and worst-case modeling input assumptions.
Freeways and Arterials. Table B-1, attached, shows the conditions for urban and rural arterials and freeways that would meet the one- and eight-hour NAAQS and would be covered by this PA3. The table shows one-hour concentrations, not including background concentrations. The populated cells of the table correspond to the lane and grade combinations for arterials and freeways which, even under worst-case conditions, would not result in exceedances of the 8-hour NAAQS for CO. Where the table entries are blank, the corresponding configuration would not meet the NAAQS based on worst-case modeling and would not be covered by this PA. Project-specific modeling would typically need to be conducted to show compliance with the NAAQS in these cases. For example, for a transportation improvement project for a freeway for which the build scenario has 10 total lanes, average road grades of 2% or less, and peak hour (congested) operating speeds of 50 mph, Table B-1 shows a contribution of 8.0 ppm for the one-hour CO standard. Since a CO concentration is shown in the table for this project type and configuration, the project is covered by this PA and does not require project-specific modeling for CO. Conversely, the same freeway with 12-lanes would not be covered by this PA, as the table entry is blank for that configuration. The values shown in Table B-1 were determined using conservative or worst-case modeling inputs and assumptions for MOVES and CAL3QHC (see Technical Approach discussion, below). Concentrations for comparison to the eight-hour NAAQS were determined from the one-hour values shown using a national average eight-hour background concentration of 2.6 ppm along with the EPA recommended persistence factor of 0.7. The resulting eight-hour concentrations were used to identify which arterial and freeway configurations would meet the eight-hour NAAQS. Note: this PA covers lanes widths of 11 feet or more for freeway and arterial project types.
