Title 23
SECTION 490.513
490.513 Calculation of National Highway System performance measures.
§ 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”; SLi = length, to the nearest
thousandth of a mile, of Interstate System reporting segment “i”;
AVi = 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; OFi = 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”; SLi = length, to the nearest thousandth of a mile, of
non-Interstate NHS reporting segment “i”; AVi = 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; OFj = 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. [82 FR 6031, Jan. 18, 2017, as amended at 83 FR 24936,
May 31, 2018]