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57 CHAPTER 6 Improving Airport Curbside and Terminal Area Roadway Operations This chapter presents examples of commonly occurring air- commonly occurring airport curbside and terminal area port curbside and roadway operational problems and poten- roadway operations. Tables 6-1 and 6-2 present commonly tial improvement measures. occurring problems and potential improvement measures Analyses and evaluations of airport curbside and terminal for terminal area roadways and curbsides, respectively. area roadways generally involve the following steps: These tables also indicate the relative benefits resulting from implementation of the improvement, although the 1. Identify the Problem(s)--Problem identification includes actual benefits will vary significantly depending on the road- determining the causes of existing congestion, delays, way configuration and nature of the problem at the specific imbalances in demand, and/or whether the existing (or airport. proposed) roadway network can accommodate anticipated 4. Evaluate the Potential Improvements--The alternative future requirements. analytical methods described in previous chapters can be 2. Document Goals and Objectives--Documenting the rele- used to quantify the changes expected to result from the vant goals and objectives of airport management (and other potential improvements, to assess their advantages and dis- stakeholders) with respect to roadway operations is a key advantages, and to identify the preferred improvement(s). step in the analysis and evaluation process. The relevant 5. Reach Consensus on the Preferred Improvement--A key objectives may include such broad categories as step in the implementation process is to build consensus Providing safe and secure operations for airport users; supporting the selection and implementation of the pre- Providing desired levels of customer service for airline ferred alternative. An evaluation process that quantifies the passengers, visitors, employees, and other airport users; extent to which the potential improvement would support Accommodating existing and future requirements; the stated goals and objectives of airport management (and Accommodating regional mobility needs/encouraging other stakeholders) provides a foundation for achieving the use of public transportation; consensus. Supporting regional air quality goals; 6. Implement the Preferred Solution--This step could Supporting the airport's ability to maintain or enhance involve design and construction activities, operational airfield capacity by ensuring that changes to roadways improvements, or changes in airport management policies. and curbsides do not negatively affect airfield opera- tions or capacities; and Typical Terminal Area Maintaining and enhancing the net revenues generated Roadway Problems by the airport. Detailed descriptions and definitions of goals will allow Operational and physical problems can adversely affect the the development of airport-specific objectives that can be ability of terminal area roadways to accommodate traffic effi- used to compare and evaluate alternative improvement ciently and safely. In this section, 10 types of deficiencies that measures. may occur in an airport environment are identified. These defi- 3. Identify and Develop Potential Improvements--The ciencies typically can result in queues or delays; many airport potential improvement measures described in this chapter roadways exhibit one or more of the deficiencies described in can serve as a starting point for improvements that address this section.

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58 Table 6-1. Typical terminal area roadway problems and improvement measures. Note: Relative success of an improvement measure may vary significantly depending upon factors unique to an individual airport. Table 6-2. Typical curbside roadway problems and improvement measures. Note: Relative success of an improvement measure may vary significantly depending upon factors unique to an individual airport.

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59 Insufficient Roadway Capacity the diverge point that allows motorists access to either of the two downstream roadways (e.g., an "either-or" lane) or by A roadway has insufficient capacity if, during the analysis extending a lane downstream past the merge/diverge point and period, the roadway operates at LOS D or worse (see Chapters then dropping the lane using design guidelines appropriate for 4 and 5 for definitions of levels of service). LOS D refers to con- the roadway speed (e.g., taper distances). gested roadways and is an unacceptable basis for planning air- port roadways. Specific implications of insufficient roadway Directional Information Overload capacity include (1) congested roadway sections with queues extending to upstream roadways, (2) motorists experiencing Directional or wayfinding information overload occurs frequent congestion and significant delays, and (3) a generally when more information (or decisions) is presented to a unsatisfactory airport experience. motorist than the motorist can read, comprehend, and react to in the available time (and distance). This overload causes driv- Insufficient Merging Capacity ers to weave suddenly, miss exits, make sudden or erroneous movements, or, in extreme cases, stop in the roadway (or on Insufficient merging capacity results when a roadway does the shoulder) to read the signage. not provide sufficient capacity at points where two or more It is desirable to avoid presenting more than two decisions streams of traffic combine into a single stream. This deficiency or more than four lines of text on each directional sign. If more results in roadway delays, congestion, and traffic queues than four lines of text must be used on one sign at an airport, extending back from the merge point. Merge segment capac- it is necessary to prioritize the information and avoid using ity is determined by the volume of entering traffic, operating unfamiliar or inconsistent terms. speeds, and number of lanes upstream and downstream. Insufficient Decision-Making Distance Inadequate Weaving Distance Insufficient decision-making distance is defined as an insuf- Inadequate weaving distance results when a roadway does ficient distance (or time) for motorists to read, comprehend, not provide sufficient length or travel lanes to accommodate and react to information regarding a decision that must be the traffic volumes at the point where two or more streams of made. This situation causes drivers to weave suddenly, miss traffic traveling in the same direction cross or merge, causing exits, make wrong turns, or, in extreme cases, stop in the road- vehicles to decelerate (or stop) while waiting for adequate way to read the message or back up to the decision point. Fac- gaps in the traffic stream. This deficiency results in (1) vehicle tors contributing to providing the necessary decision-making delays and queues, (2) higher accident rates, and (3) slower distance include travel speed, message content, visibility of the speeds and flow rates. Factors influencing required weaving dis- decision point, and visibility of the directional signage. tances are operating speeds, traffic volumes (merging, weaving, and flowing through the segment), and the number of lanes that Insufficient Queuing Space vehicles must cross to complete the desired maneuver. Queuing space represents the area required to accommodate Lane Imbalance vehicles stopped at an entrance (or exit) to a parking lot or other facility, traffic signal or turn lane, or vehicle inspection Lane imbalance results when a roadway segment, before a area so that vehicles in the queue do not interfere with traffic diverge or after a merge, contains two (or more) fewer lanes flow on the adjacent roadway or travel lanes. For example, a than the combined total number of lanes entering or exiting parking facility entrance should have sufficient space to accom- the segment. For example, at a point where two three-lane modate vehicles queuing at the ticket issuing machines with- roadways merge, the downstream segment must consist of at out having the queue extend onto the adjacent roadway. (See least five lanes or a lane imbalance will result. At a point where Figure 6-1.) a roadway diverges into two two-lane roadways, the upstream segment (prior to the diverge) must consist of at least three Unexpected Lane Drops/Inadequate lanes. A lane imbalance can cause increased delays, sudden Taper Lengths diverge or weave maneuvers, increases in the required roadway weaving distances (e.g., the number of lanes to be crossed), and Unexpected lane drops and inadequate taper lengths (the higher accident rates. Proper lane balance helps reduce or avoid distance required to introduce a new lane or drop an exist- forced merges, weaves, and sudden maneuvers. For example, ing lane) result when a through lane unexpectedly ends and when a two-lane roadway splits or diverges into two roadways, motorists are required to unexpectedly merge quickly into an lane balance can be achieved by providing a third lane prior to adjacent lane. Required taper lengths, which vary according to