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CHAPTER 2
State of the Practice
This chapter summarizes the state of the practice in the LOS A averages about 85% of the typical mid-block free-flow
United States with regard to multimodal LOS analysis and speed, LOS B averages 67%, LOS C averages 51%, LOS D
identifies needed improvements. The review includes national averages 39%, and LOS E averages 29%.
and state guides on LOS analysis and profiles of typical and The HCM provides a methodology for estimating the
state-of-the-art applications of modal and multimodal LOS by mean speed for through traffic on an urban street. The
public agencies in the United States. methodology reduces the mid-block free-flow speed accord-
ing to the average delay to through traffic at each traffic signal.
This speed is further reduced to account for delays between
2.1 State-ofthe-Practice Survey
signals due to short signal spacing (called "segment running
A brief state-of-the-practice survey was conducted of a few time" in the HCM). The effects of signal progression are
selected representative public agencies to determine how taken into account in the computation of mean delay at each
public agencies currently use level of service. Exhibit 1 lists signal.
the people and agencies contacted. For comparison with the other model forms discussed
The state-of-the-practice survey identified three major later, the HCM look-up table can be expressed (approxi-
professional manuals typically referenced by public agencies mately) in the form of a linear function of facility type and
when computing multimodal highway level of service. These speed, as follows:
manuals are the Highway Capacity Manual [1], the Transit
LOS = Integer{0.151231 * Speed
Capacity and Quality of Service Manual [2], and Florida's
+ 0.636927 * Class - 2.17765} (Eq. 1)
Quality/Level of Service Handbook [3]. The portions of these
manuals relevant to the current research are summarized in Where
the following subsections. LOS = HCM LOS Integer Scale (where A=5, F = 0)
Integer = The integer function (rounds off the value to the
nearest integer value).
Highway Capacity Manual
Speed = Mean speed of through traffic on arterial in mph.
The Highway Capacity Manual (HCM) provides LOS Class = Arterial Class as defined by HCM (Class 1, 2, 3,
measures, thresholds, and estimation procedures for auto, or 4)
transit, bicycle, and pedestrian modes. (R-Square = 0.97, all variables significant)
Urban Street LOS Transit LOS
Chapter 15 of the HCM defines urban street LOS according Chapter 27 of the HCM provides four transit LOS measures,
to the mean speed of through traffic on an urban street. The pre- adapted from the six presented in the Transit Capacity and
cise thresholds vary by urban street class (see Exhibit 2), which Quality of Service Manual, First Edition: Service Frequency,
affects the presumed mid-block free-flow speed on each street. Hours of Service, Passenger Load, and Service Reliability.
When one takes into account the differing typical free-flow These measures are presented below under the Transit Capac-
speeds for the urban street classes, the speed breakpoint for ity and Quality of Service Manual section.
