23 CFR § 490.711 - Calculation of Peak Hour Excessive Delay metric.
(a) The performance metric required to calculate the measure specified in § 490.707(a) is Total Peak Hour Excessive Delay (person-hours)(referred to as the PHED metric). The following paragraphs explain how to calculate this PHED metric.
(b) State DOTs shall use the following data to calculate the PHED metric:
(1) Travel times of all traffic (“all vehicles” in NPMRDS nomenclature) during each 15 minute interval for all applicable reporting segments in the travel time data set occurring for peak periods from January 1st through December 31st of the same year;
(2) The length of each applicable reporting segment, reported as required under § 490.709(b);
(3) Hourly volume estimation for all days and for all reporting segments where excessive delay is measured, as specified in § 490.709(c);
(4) Annual vehicle classification data for all days and for all reporting segments where excessive delay is measured, as specified in § 490.709(d); and
(5) Annual vehicle occupancy factors for cars, buses, and trucks for all days and for all reporting segments where excessive delay is measured, as specified in § 490.709(e).
(c) The State DOT shall calculate the “excessive delay threshold travel time” for all applicable travel time segments as follows:
(d) State DOTs shall determine the “excessive delay” for each 15 minute bin of each reporting segment for every hour and every day in a calendar year as follows:
(1) The travel time segment delay (RSD) shall be calculated to the nearest whole second as follow:
(2) Excessive delay, the additional amount of time to traverse a travel time segment in a 15-minute bin as compared to the time needed to traverse the travel time segment when traveling at the excessive delay travel speed threshold, shall be calculated to the nearest thousandths of an hour as follows:
(e) State DOTs shall use the hourly traffic volumes as described in § 490.709(c) to calculate the PHED metric for each reporting segment as follows:
AVO = (PC × AVOC) + (PB × AVOB) + (PT × AVOT)
(f) Starting in 2018 and annually thereafter, State DOTs shall report the PHED metric (to the nearest one hundredth hour) in accordance with HPMS Field Manual by June 15th of each year for the previous year's PHED measures. The PHED metric shall be reported for each reporting segment. All reporting segments of the NPMRDS shall be referenced by NPMRDS TMC or HPMS section(s). If a State DOT elects to use, in part or in whole, the equivalent data set, all reporting segments shall be referenced by HPMS sections.