LOS for freeway facilities is based on the facility-wide average density expressed in pcpmpl. There are separate density thresholds for urban and rural locations. The LOS for an overall freeway facility is typically accompanied by the LOS for the individual segments. LOS for basic freeway segments, weaving segments, merge, and diverge segments are also based on density. The LOS thresholds apply to both urban and rural locations. The thresholds for weaving segments are higher than basic segments because drivers tolerate higher density in areas where lane-changing is expected. Supplemental information with

example

applications are provided in HCM 7th Edition Chapter 25 (freeway facilities), Chapter 26 (freeway and highway segments), Chapter 27 (freeway weaving), and Chapter 28 (freeway merges and diverges). For LOS criteria of various freeway facilities see

Table 9-6

,

Table 9-7

,

Table 9-8

,

and

Table 9-9

.

The LOS thresholds for multi-lane highway segments are the same as basic freeway segments. The thresholds for weaving segments on multi-lane highways, however, are different than the thresholds for freeway weaving segments, as presented in

Table 9-10

. The LOS criteria for freeway merge and diverge segments are used for merge and diverge segments on multi-lane highways. See for HCM’s LOS criteria for multi-lane highways.

LOS criteria for two-lane highways are based on three performance measures: ATS, PTSF, and PFFS. ATS is the segment length divided by average travel time for the segment. See

Chapter 4

for definitions of PFFS and PTSF. Additional information, with

example

applications, is available in HCM 7th Edition Chapter 26 (freeway and highway segments), Chapter 27 (freeway weaving), and Chapter 28 (freeway merges and diverges). See

Table 9-11

for the LOS criteria for two-lane highways in the HCM.

The LOS thresholds for urban arterial segments are based on travel speed of the vehicles traveling through the segment. HCM-based (mesoscopic) analyses are applicable for arterial and collector street segments with a length of two miles or less. If a segment is longer than two miles between boundary intersections, it is recommended that it is treated as a highway and the intersections are studied individually. If the segment being studied has intersections along its length, the speed and travel times of vehicles is largely dependent on intersection delay. Supplemental information with

example

applications is found in HCM 7th Edition Chapter 29 (Urban Street Facilities: Supplemental) and Chapter 30 (Urban Street Segments: Supplemental).

Table 9-12

shows the LOS criteria for urban arterial segments.

The LOS of frontage roads is based on the ATS of vehicles traveling through the segment, which is a function of segment length and total travel time. Travel time is estimated using TTI’s procedures or measured directly in the field. For an analysis requiring medium amounts of detail, it is recommended that travel time be estimated using TTI’s procedures or calculated using HCS or similar software. Travel time is a function of running time (the time it takes to travel a segment), intersection delay, and ramp delay. Factors that influence the operations of a frontage road include the intersections along the segment and the driveways along the segment