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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Project 21 -N-controlo Surface Demo</title>
      <link>https://rip.trb.org/View/1364486</link>
      <description><![CDATA[Taxiing aircraft contribute significantly to fuel burn and emissions at airports. The quantities of fuel burned as well as different pollutants, such as carbon dioxide, hydrocarbons, nitrogen oxides, sulfur oxides and particulate matter, are functions of aircraft taxi duration (along with throttle setting, number of running engines, and pilot and airline decisions regarding engine shutdowns during delays). The reduction of taxi times through improved planning of surface movements has the potential to reduce these emissions. Project 21 focuses on opportunities to reduce surface emissions through departure planning and surface movement optimization. The research will include a detailed plan for implementing these techniques in a pilot study at an airport, with an overall goal of initiating wider adoption of the methods throughout the United States. This project will investigate approaches, such as gate-holds and taxi-route planning, to decrease taxi times. In addition, environmental factors will be incorporated into the objective functions of the optimization through the use of aircraft-specific delay costs, which will reflect the fact that the emissions characteristics of various aircraft may differ. Current baseline fuel burn and emissions at major airports will also be assessed in order to identify locations where the proposed strategies will produce the most benefits. Project 21 will also address the development of approaches to surface movement optimization that will balance both airport throughput and emissions objectives, while simultaneously ensuring fairness in the delays incurred by the different airlines. Barriers to the practical adoption of these approaches, such as gate usage and ownership issues, as well as surface infrastructure considerations such as taxiway layouts, the availability of tugs, and the presence and location of holding areas, will be identified, and possible approaches to overcome these barriers will be developed. Airline competition, tradeoffs between airline and air traffic control objectives, traffic flow management initiatives in the airspace and the presence of uncertainty in airport processes (which result in uncertain estimates of pushback times and taxi times) also pose significant challenges to surface movement optimization, and will be addressed.]]></description>
      <pubDate>Sat, 08 Aug 2015 01:02:00 GMT</pubDate>
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      <title>System Level Implications of Changes in Future Aircraft Mission Specifications</title>
      <link>https://rip.trb.org/View/1363272</link>
      <description><![CDATA[Future reductions of fuel burn and green house gas emissions from commercial aviation will be, in large part, achieved through the development and use of more fuel- and environmentally-efficient aircraft. Achieving significant efficiency improvements at the aircraft level may require opening up the design space so as to consider changes in aircraft design mission specifications/capabilities such as lower cruise speed, different payload-range characteristics, and longer wing span. However, there are potentially serious and unforeseen system-wide implications (economics, viability, delays, manufacturability, etc.) that could result from these changes and that have not yet been quantified properly. The main objective of this project is to understand and quantify these implications so that informed decisions can be made.]]></description>
      <pubDate>Wed, 29 Jul 2015 01:00:46 GMT</pubDate>
      <guid>https://rip.trb.org/View/1363272</guid>
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      <title>System Level Implications of Changes in Future Aircraft Mission Specifications</title>
      <link>https://rip.trb.org/View/1363056</link>
      <description><![CDATA[Future reductions of fuel burn and green house gas emissions from commercial aviation will be, in large part, achieved through the development and use of more fuel- and environmentally-efficient aircraft. Achieving significant efficiency improvements at the aircraft level may require opening up the design space so as to consider changes in aircraft design mission specifications/capabilities such as lower cruise speed, different payload-range characteristics, and longer wing span. However, there are potentially serious and unforeseen system-wide implications (economics, viability, delays, manufacturability, etc.) that could result from these changes and that have not yet been quantified properly. The main objective of this project is to understand and quantify these implications so that informed decisions can be made.]]></description>
      <pubDate>Sat, 25 Jul 2015 01:00:35 GMT</pubDate>
      <guid>https://rip.trb.org/View/1363056</guid>
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    <item>
      <title>Opportunities for Reducing Surface Emissions through Airport Surface Movement Optimization</title>
      <link>https://rip.trb.org/View/1362886</link>
      <description><![CDATA[Taxiing aircraft contribute significantly to fuel burn and emissions at airports. The quantities of fuel burned as well as different pollutants, such as carbon dioxide, hydrocarbons, nitrogen oxides, sulfur oxides and particulate matter, are functions of aircraft taxi duration (along with throttle setting, number of running engines, and pilot and airline decisions regarding engine shutdowns during delays). The reduction of taxi times through improved planning of surface movements has the potential to reduce these emissions. Project 21 focuses on opportunities to reduce surface emissions through departure planning and surface movement optimization.]]></description>
      <pubDate>Fri, 24 Jul 2015 01:00:44 GMT</pubDate>
      <guid>https://rip.trb.org/View/1362886</guid>
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