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CHAPTER 4
Analyzing Airport Terminal Area Roadways
This chapter presents an overview of terminal area roadway Level-of-Service Definitions for
analyses. It presents level-of-service definitions applicable to Airport Terminal Area Roadways
airport roadways and describes methods for estimating the
The key performance measures defining the level of service
capacity and levels of service. Chapter 5 presents comparable
of an airport terminal area roadway are as follows:
methods for analyzing curbside roadways.
As described earlier, a hierarchy of analytical methods-- · Average speed, which determines travel time;
including quick-estimation, macroscopic, and microsimula- · Traffic density, which determines the ability of motorists
tion methods for analyzing airport terminal area roadway and to easily maneuver into and out of travel lanes;
weaving section operations, is proposed. The appropriate ana- · Maximum volume-to-capacity (v/c) ratio, which indicates
lytical method will evolve as a project proceeds from concept how close the roadway is to breakdown and is useful for
to final design, and as more time and data become available to determining other performance measures such as queue
support the analyses. length and delays; and
This chapter presents the suggested quick-estimation meth- · Duration and length of queues.
ods for analysis of airport roadways with uninterrupted flows, With the exception of the weaving analysis discussed in this
signalized roadways, and airport roadway weaving sections; the chapter, the definitions, metrics, and procedures presented
macroscopic method for analyzing low-speed roadway weav- in the 2000 HCM are applicable to airport roadways with un-
ing areas commonly found on airports; and an overview of the interrupted operations and signalized and unsignalized (i.e.,
use of microsimulation methods. stop-sign controlled) intersections.
The macroscopic methods and performance measures The weaving analysis methods presented in the 2000 HCM
presented in the 2000 HCM are considered applicable for (and the 2010 update) are primarily oriented toward opera-
analyses of airport roadways with uninterrupted traffic tions on freeways or major arterial streets. At airports, weaving
flows and unsignalized or signalized intersections, but not often takes place on roadway segments designed for speeds that
for analyses of low-speed roadway weaving areas. It is sug- are much slower than those on freeways or even on major arte-
gested that the method presented in the section on Macro- rial streets. As a result, although the weaving theory and meth-
scopic Method for Analyzing Airport Roadway Weaving ods presented in the 2000 HCM (and subsequent updates) are
Areas be used when macroscopic analyses of airport weav- applicable to airport roadways, the metrics defining levels of
ing areas are required, and that the methods presented in service are not. Consequently, subsequent portions of this
chapter present alternative metrics for the low-speed weaving
the HCM be used for macroscopic analyses of all other air-
that occurs on airport roadways.
port roadways.
The methods and data presented in this chapter represent
the best available information concerning airport roadway
Quick-Estimation Methods for
Analyzing Airport Roadway
operations and the consensus of the research team, the Project
Operations
Panel, and other reviewers at the time this Guide was prepared.
It is suggested that additional research be conducted on low- This section presents quick-estimation methods for ana-
speed weaving areas and maximum service rates for airport lyzing uninterrupted flows, signalized roadways, and airport
roadways. roadway weaving sections.
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Quick-Estimation Method for Uninterrupted adjusted flow rates for multilane roadways with uninter-
Flows on Airport Roadways rupted flows. The adjusted flow rates represent the maximum
flow rates of typical airport access and circulation roadways
Quick-estimation methods are most appropriate for "siz- and were calculated assuming that (1) heavy trucks and buses
ing" a roadway in the early stages of planning and the design represent less than 5% of the traffic volume on the access
process when little has been decided (or is known) about the roadways, (2) courtesy vehicles and minibuses (which are
details of the required roadway. Such methods are suitable for assumed to be equivalent to recreational vehicles in terms of
use when preparing airport master plans or terminal area performance) represent about 10% of the traffic volume on
plans to size or evaluate a roadway and identify points of access roadways, and (3) a high proportion of drivers who are
existing or future constraints. infrequent users of, and are, therefore, unfamiliar with, the
Table 4-1, which is adapted from Exhibits 21-2 and 21-3 of airport roadways. The free-flow speeds can be approximated by
the 2000 HCM, presents the maximum service flow rate and the posted speed limits on the roadway section unless drivers
Table 4-1. Levels of service for airport terminal area access and
circulation roadways.
Level of service
Criteria A B C D E
Free-flow speed = 50 mph
Minimum speed (mph) 50.0 50.0 50.0 48.9 47.5
Maximum volume/capacity ratio 0.28 0.45 0.65 0.86 1.00
Maximum service flow rate (passenger cars/
hour/lane) 550 900 1,300 1,710 2,000
Maximum flow (vehicles/hour/lane) (a) 440 730 1,050 1,380 1,620
Free-flow speed = 45 mph
Minimum speed (mph) 45.0 45.0 45.0 44.4 42.2
Maximum volume/capacity ratio 0.26 0.43 0.62 0.82 1.00
Maximum service flow rate (passenger cars/
hour/lane) 490 810 1,170 1,550 1,900
Maximum flow (vehicles/hour/lane) (a) 400 650 940 1,250 1,530
Free-flow speed = 40 mph
Minimum speed (mph) 40.0 40.0 40.0 39.0 38.0
Maximum volume/capacity ratio 0.26 0.42 0.61 0.82 1.00
Maximum service flow rate (passenger cars/
hour/lane) 450 740 1,060 1,400 1,750
Maximum flow (vehicles/hour/lane) (a) 360 600 860 1,130 1,410
Free-flow speed = 35 mph
Minimum speed (mph) 35.0 35.0 34.0 34.0 33.0
Maximum volume/capacity ratio 0.26 0.42 0.61 0.80 1.00
Maximum service flow rate (passenger cars/
hour/lane) 410 670 980 1,280 1,600
Maximum flow (vehicles/hour/lane) (a) 330 540 790 1,030 1,290
Free-flow speed = 30 mph
Minimum speed (mph) 30.0 30.0 30.0 29.6 29.0
Maximum volume/capacity ratio 0.26 0.41 0.60 0.79 1.00
Maximum service flow rate (passenger cars/
hour/lane) 370 600 870 1,150 1,450
Maximum flow (vehicles/hour/lane) (a) 300 480 700 930 1,170
Free-flow speed = 25 mph
Minimum speed (mph) 25.0 25.0 25.0 24.8 24.0
Maximum volume/capacity ratio 0.25 0.40 0.59 0.79 1.00
Maximum service flow rate (passenger cars/
hour/lane) 310 500 740 990 1,250
Maximum flow (vehicles/hour/lane) (a) 250 400 600 800 1,010
mph = miles per hour
(a) Flow rates adjusted to account for 0.95 heavy vehicle factor and 0.85 driver population factor due to
occasional or unfamiliar users.
Source: LeighFisher, based on information presented in Transportation Research Board, National
Research Council, Highway Capacity Manual, Exhibits 21-2 and 21-3, December 2000.
