Code of Federal Regulations Title 23. Highways § 490.513.Calculation of National Highway System performance measures

(a) The NHS Performance measures in § 490.507 shall be calculated in accordance with this section by State DOTs and MPOs to carry out the Interstate System and non–Interstate NHS performance-related requirements of this part, and by FHWA to make the significant progress determinations specified in § 490.109 and to report on system performance.

(b) The Interstate Travel Time Reliability measure specified in § 490.507(a)(1) shall be computed to the nearest tenth of a percent as follows:

Where:

R = total number of Interstate System reporting segments that are exhibiting an LOTTR below 1.50 during all of the time periods identified in § 490.511(b)(1)(i) through (iv);

I = Interstate System reporting segment “i”;

SL_i = length, to the nearest thousandth of a mile, of Interstate System reporting segment “i”;

AV_i = total annual traffic volume to the nearest single vehicle, of the Interstate System reporting segment “i”;

J = geographic area in which the reporting segment “i” is located where a unique occupancy factor has been determined;

OF_i = occupancy factor for vehicles on the NHS within a specified geographic area within the State/Metropolitan planning area; and

T = total number of Interstate System reporting segments.

(c) The Non–Interstate Travel Time Reliability measure specified in § 490.507(a)(2) shall be computed to the nearest tenth of a percent as follows:

Where:

R = total number of non–Interstate NHS reporting segments that are exhibiting an LOTTR below 1.50 during all of the time periods identified in § 490.511(b)(1)(i) through (iv);

i = non–Interstate NHS reporting segment “i”;

SL_i = length, to the nearest thousandth of a mile, of non–Interstate NHS reporting segment “i”;

AV_i = total annual traffic volume to the nearest 1 vehicle, of the Interstate System reporting segment “i”;

j = geographic area in which the reporting segment “i” is located where a unique occupancy factor has been determined;

OF_j = occupancy factor for vehicles on the NHS within a specified geographic area within the State/Metropolitan planning area; and

T = total number of non–Interstate NHS reporting segments.

(d) The GHG measure specified in § 490.507(b) shall be computed to the nearest tenth of a percent as follows:

Where:

(Tailpipe CO₂ Emissions on NHS)_CY = total tailpipe CO₂ emissions on the NHS in a calendar year (expressed in million metric tons (mmt), and rounded to the nearest hund redth); and

(Tailpipe CO₂ Emissions on NHS)_reference year = total tailpipe CO₂ emissions on the NHS in calendar year 2022 (expressed in million metric tons (mmt), and rounded to the nearest hundredth).