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Figure 6-1. Insufficient queuing space at parking entry at Tulsa International Airport.
roadway operating speeds, are intended to allow sufficient network. If a movement is missing, motorists may need to exit
distance for lane channelization and vehicle merging. Un- and re-enter the airport or travel extra distance. For example,
expected lane drops reduce roadway capacity and travel speeds, at most major airports, motorists can proceed directly from the
as motorists who become "trapped" in a lane are required to enplaning curbside to short-duration parking and from short-
merge quickly (interfering with the flow of other vehicles in duration parking to the deplaning curbside without leaving
adjacent lanes). the terminal area. The absence of roadway segments provid-
ing these direct movements increases traffic demand on the
Unexpected Transition from High-Speed return-to-terminal roadways and vehicle miles of travel.
to Low-Speed Roadway Environment
Potential Terminal Area Roadway
Some motorists do not realize they need to slow down as
Improvement Measures
they exit from a regional roadway (which may operate at more
than 55 mph) and approach a terminal area roadway (which Potential improvements to terminal area roadway opera-
may operate at less than 30 mph) until they encounter a sharp tions are presented in the following categories:
curve at the entrance to the terminal or vehicles stopped in
the roadway. This situation is particularly true at airports · Physical improvements,
where a limited access highway, designed to freeway stan- · Operational measures, and
dards and capable of accommodating freeway speeds, connects · Airport policies.
the regional roadway network with the terminal area roadways
(see Figure 6-2). Motorists may be provided few visual clues
that the driving environment is changing and requires them to
decelerate. Additionally, speed limit signs may get lost among
the many other signs and distractions associated with roadways
approaching an airport terminal.
This transition is compounded by the reduction in roadway
capacity that accompanies the reduction in speed: a three-lane
access roadway operating at 55 mph (or more) has more capac-
ity than a three-lane curbside roadway operating at 30 mph (or
less). If the traffic volume on the access roadway is the same as
that on the curbside roadway, it is necessary to provide addi-
tional travel lanes on the curbside roadway to compensate for
the reduction in travel speed. Often, the volumes are not con-
stant, as some traffic exits for non-terminal area destinations,
such as parking and rental car facilities.
Missing Movements
Figure 6-2. Transition from high-speed to low-speed
Missing movements are defined as a desired travel path or airport roadways at Baltimore/Washington
traffic movement that is not provided on an airport roadway International Thurgood Marshall Airport.
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A general planning principle for the design and operation listed in Appendix B, including those published by AASHTO,
of airport roadways is to separate traffic generated by airline provide additional information on this topic.
passengers and visitors from that generated by employees, · Adding exclusive left- or right-turn lanes. The capacity of
air cargo, and services or deliveries. At airports with multi- at-grade intersections, particularly signalized intersections,
ple entrances/exits, this can be accomplished by having one can be improved by providing exclusive left-turn lanes
entry/exit serving airline passengers and the other serving non- (thereby eliminating conflicting traffic movements from a
passenger traffic. At airports with one access road, this can be signal phase) or adding free-flow right-turn lanes.
accomplished by having nonpassenger traffic exit the access
roadway well in advance of the terminal area, and by provid- Reconfigure Roadways
ing a separate service roadway for these vehicles.
Appendix B (Bibliography) lists selected references regarding · Eliminating three-way decision points. It may be possible
the design and improvement of roadways and intersections to eliminate a three-way decision point without requiring
and relevant design standards and guidelines relevant to air- major roadway reconstruction, by moving one of the deci-
ports. These references should be reviewed prior to implement- sion points upstream and thereby converting the three-way
ing any roadway improvement, particularly those that require decision point into two separate two-way decision points,
the design of new roadways or modification or reconfiguration which is preferable and easier for motorists.
of the layout of existing roadways. · Lengthening weaving area. It may be possible to improve
an unacceptable weaving operation by closing one exit from
the weaving area and directing traffic to a subsequent down-
Potential Physical Improvements stream exit leading to the same destination. For example, at
to Enhance Roadway Operations Seattle-Tacoma International Airport, traffic operations on
Widen Roadways a return-to-terminal roadway were improved by directing
recirculating traffic toward the airport exit and then to a
Additional roadway capacity can result from the following: path that leads back to the terminal, thereby extending the
length of the weaving area. At Los Angeles International
· Constructing new lane(s). Additional lanes can be con-
Airport, a movable gate arm is used to close a roadway to
structed if sufficient available right of way is clear (or if it can traffic on the busiest days of the year, requiring vehicles to
be cleared) of obstacles, such as existing or proposed build- follow a slightly longer path, but extending the length of the
ings, underground utilities, aviation limit lines (where FAA weaving area. Such improvements can be implemented for
restrictions govern acceptable land uses), or other fixed minimal cost (e.g., replacing a roadway directional sign and
obstacles. Construction costs and schedules are a function of installing a barrier, if necessary).
the roadway alignment, extent and type of construction, · Improving queuing space. Queuing space can be improved
obstacles to be relocated (if any), need to maintain and pro- by either providing additional storage space or increasing
tect other vehicular and pedestrian traffic during construc- flow rates through the point of constraint. For example at
tion, and other factors. the entry or exit of a parking facility, queuing space can be
· Reconfiguring existing lanes. Additional lanes can be cre- increased (1) by relocating the gate arms at the entry or con-
ated by reducing the widths of existing roadway lanes to trol booths at the exit plaza to provide additional storage
form additional lanes. For example, five lanes can be cre- space or (2) by increasing traffic flow rates at the control
ated on an existing four-lane roadway by reducing lane point by replacing the existing access control technology
widths (e.g., from 13 feet or 12 feet to 11 feet or 10 feet) and (e.g., replacing an existing ticket issuing machine with a
by simultaneously reducing the width of, or converting, card reader recognizing employee parking badges, or an
roadway shoulders or paved gutter strips into travel lanes. automatic vehicle identification [AVI] transponder on
Unless existing drainage structures must be replaced or commercial ground transportation vehicles). For example,
relocated, the cost of such reconfiguration is very low. with use of a credit card in/credit card out parking access
· Lengthening tapers/correcting lane imbalances. Roadway control system, more vehicles can be processed per lane
construction is required to correct inadequate roadway than with a cashier, and the need to print and issue parking
tapers or lane imbalances. The length of a roadway taper tickets may be reduced or potentially eliminated.
depends on the posted speed. For example, a 250-foot-long
taper is required on a 35 mph roadway to add (or end) a
Improve Roadway Wayfinding Signs
12-foot-wide travel lane. Providing the required lane bal-
ance may require construction of a full lane (upstream or It may be possible to improve roadway guide signs by
downstream) for a longer distance. Highway design guides replacing complex, existing signs with simpler signs that can
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be more easily understood by motorists. This can be accom- of concrete pavement to create a warning signal (i.e., a rum-
plished by attempting to simplify and prioritize the message ble strip) for motorists as they approach a slow-speed area.
content, reviewing the text and font, and using standard It is possible to increase the frequency and volume of the
phraseology where possible. The use of dynamic message signs warning signal by reducing the distance between successive
may also be helpful in certain instances (e.g., parking controls strips.
and space availability). · Dynamic warning signs. Radar-activated speed limit signs
can be installed to detect the speed of approaching vehicles
and indicate to drivers how fast they are traveling. For
Construct and Operate Traffic Operations Center
vehicles exceeding the posted speed limit, the display could
At airports with complex roadway networks and multiple flash red.
parking facilities, it may be possible to improve traffic flows by · Automatically activated pedestrian signals. Pedestrians
constructing and operating a traffic operations center, simi- crossing a roadway can automatically activate signals embed-
lar to those in many large urban areas (see Figure 6-3). Using ded in the roadway pavement.
video cameras, traffic detectors, and other technologies, the · Enforcement. Police enforcement measures and tools that
traffic operations center allows airport staff to monitor air- are commonly and frequently used in non-airport environ-
portwide traffic operations, direct airport traffic officers to ments can be used to enforce posted speeds, including park-
congestion points, close or open parking facilities or road- ing police vehicles in a visible location.
ways, change advisory signs, and perform other operations to
improve the flow of traffic.
Transportation Demand Management
When used in an urban or regional setting, transportation
Potential Operational Measures to Enhance
demand management (TDM) measures are used to discourage
Roadway Operations
single-occupant, private vehicle trips by promoting ride-
Speed Reduction Measures sharing or the use of public transit, and to encourage motorists
to drive outside peak hours. At airports, the most productive
It may be necessary to encourage motorists to decelerate as
application of TDM is to encourage airport employees to share
they approach the terminal area, particularly at airports where
rides or use public transit to reduce the number of vehicle trips.
a limited access highway connects the regional roadway net-
For example, some airport operators and other employers have
work with the terminal area roadways.
established work schedules that call for employees to work 9
Measures to encourage motorists to obey posted speed lim-
out of every 10 days (e.g., take every other Friday off by work-
its and slow down as they approach the terminal area include
ing longer hours on other days). Other airport operators offer
discounted transit passes or partially subsidize the commuting
· Pavement texture. Contrasting pavement textures (e.g.,
expenses of employees who agree to use transit and forego the
brick, cobblestone, or gravel textures) can be cast into strips
use of parking facilities.
Intelligent Transportation Systems
A variety of intelligent transportation system (ITS) applica-
tions are available to encourage the efficient and safe use of
transportation facilities. At airports these applications include
pricing mechanisms (increasing parking costs), the use of AVI
and global positioning system (GPS) technologies to monitor
the location and number of trips made by commercial vehi-
cles or shuttle buses, and a variety of systems for distribut-
ing traveler information to arriving motorists (e.g., airline
schedules/delays and parking space availability). Traveler
information can be distributed using the Internet, mobile tele-
phones, highway advisory radios, flight information display
systems (e.g., those located on deplaning curbsides or within
cell phone lots), or dynamic signage presenting parking
Figure 6-3. Transportation operations center at space availability information or warning overheight vehi-
Frankfurt Airport. cles approaching areas with limited vertical clearance.
