Abstracts: 2019-2020


Automatic Speech Recognition for Air Traffic Control Communications

Sandeep Badrinath and Hamsa Balakrishnan

A significant fraction of communications between air traffic controllers and pilots is through speech, via radio channels. Automatic transcription of air traffic control (ATC) communications has the potential to improve system safety, operational performance, and conformance monitoring, and to enhance air traffic controller training. We present an automatic speech recognition model tailored to the ATC domain that can transcribe ATC voice to text. The transcribed text is used to extract operational information such as call-sign and runway number. The models are based on recent improvements in machine learning techniques for speech recognition and natural language processing. We evaluate the performance of the model on diverse datasets.

Planning Maintenance and Rehabilitation Actions for Airport Pavements: A Combined Supervised Machine Learning and Reinforcement Learning Approach

Limon Barua

Maintenance and Rehabilitation (M&R) of airport pavement assets involves considerable financial resources. As such, even modest improvement in M&R action planning could lead to non-trivial savings. The state-of-the-practice for planning M&R actions mostly relies on condition thresholds and prioritization rules, while the state-of-the-art often requires unduly assumptions, and the computational challenge can present an important issue when characterizing pavement conditions and M&C actions involves large dimensions. This study proposes a machine learning (ML) approach that integrates pavement condition prediction using supervised ML with M&R action planning empowered by reinforcement learning (RL). The Q-learning method is used to train the RL model. The use of the integrated model is demonstrated using real-world data from the Chicago O’Hare International Airport. The results show the effectiveness of the proposed approach and potential to reduce M&R cost compared to the existing practice.


Optimization of Cellular Concrete Microstructure for Improved Impact Resistance

Jamie V. Clark and David A. Lange

Engineered material arresting system (EMAS) is a cellular concrete material currently used as passive aircraft arresting system at airports around the U.S.A. and abroad. Its cellular structure crushes on impact, helping to absorb energy and create drag resistance. Energy absorbed during crushing is defined by the load–deformation response curve, in which a plateau is indicative of crushing behavior at a near-constant load. At the microstructural level, the energy absorbed from crushing is a combination of elastic buckling, plastic yield, and brittle fracture of the cellular microstructure. Therefore, optimization of the cellular structure (e.g., bubble size and distribution) is paramount to the overall performance of these systems. This study makes use of microstructural investigations, quasi-static indentation, and drop weight testing to investigate the performance of cellular concrete with varied microstructures. The results show that, while density (air content) has been considered the main predictor of overall performance, the nature of the cellular structure created by the use of different foaming agents can be a useful design tool. This adds another critical consideration in the design of impact-resistant infrastructure. Given this finding, a new set of design guidelines are presented in this paper. This work aims to inform better design of impact-resistant infrastructure by identifying cellular concrete microstructures that lead to optimal energy absorption in low-velocity impact events, such as aircraft overruns.


Simulation Analyses of End-Around Taxiway Operations under Four Different Runway and Taxiway Choices 

Yilin Feng and Mary E. Johnson

End-around taxiways (EAT) have been implemented at four major U.S. airports to increase the safety and throughput of parallel runway systems. This paper proposes two new runway and taxiway choices that become possible because of EATs. Instead of using the inboard runway to take off, the departing aircraft could use the outboard runway and use the EAT as the taxi-out path. A discrete-event stochastic simulation model simulates the operations of four different runway and taxiway choices. Two experiments compare the performance of the four choices on average taxi times, average fuel consumption per taxi, and number of runway crossings. In general, the results indicate that using the outboard runway to take off and the EAT as a taxi-out path would yield benefits in both taxi-in and taxi-out performance, as well as enhancing runway safety. Using the outboard runway to land and the EAT as a taxi-in path would yield benefit in taxi-out performance and runway safety at the expense of a longer taxi-in time. Concerns related to using the EAT as the taxi-out path, as well as potential future research topics, are discussed.


Understanding the Role of Online Media Platforms in Airport Capital Projects and Community Outreach 

Max Z. Li and Megan S. Ryerson

Community outreach and engagement efforts are critical to an airport’s role as an ever-evolving transportation infrastructure and regional economic driver. As online social media platforms continue to grow in both popularity and influence, a new engagement channel between airports and the public is emerging. However, the motivations behind and effectiveness of these social media channels remain unclear. In this work, we address this knowledge gap by better understanding the advantages, impact, and best practices of this newly emerging engagement channel available to airports. Focusing specifically on airport YouTube channels, we first document quantitative viewership metrics, and examine common content characteristics within airport YouTube videos. We then conduct interviews and site visits with relevant airport stakeholders to identify the motivations and workflow behind these videos. Finally, we facilitate sample focus groups designed to survey public perceptions of the effectiveness and value of these videos. From our four project phases, to maximize content effectiveness and community engagement potential, we synthesize the following framework of action items, recommendations, and best practices: (C) Consistency and community; (O) Organizational structure; (M) Momentum; (B) Branding and buy-in; (A) Activity; (T) Two-way engagement; (E) Enthusiasm; and (D) Depth, or as a convenient initialism, our COMBATED framework.


Throughput Capacity Comparison for Airport Pickup and Dropoff Facilities 

Anton J. Kleywegt and Xinyu Liu

An airport serves as an interface between ground and air transportation; the efficient processing of ground transportation arrivals and departures is, therefore, an important part of airport operations. At many airports, the current pickup and dropoff locations for taxis and other passenger cars are along the terminal curb or in existing parking facilities, and many of these pickup and dropoff facilities suffer from excessive congestion. In addition, in recent years there has been growth in the use of on-demand ground transportation to and from airports, with the increased adoption of ride-hailing services, resulting in increased congestion. Since most airports are severely space constrained, there is a need to consider pickup and dropoff facilities that are more efficient (in vehicle throughput per unit space) than terminal curbs. In this paper we compare the throughput capacities of different pickup and dropoff facility layouts. We take into account the effect of the facility layout and operational rules on conflicts between the movements of different vehicles, the resulting delays in the movements of vehicles, as well as the spatial requirements of different layouts. We demonstrate the impact of mean service times, variability in service times and vehicle movement times, and operational rules on the relative throughput capacities of different facility layouts.


Economic Feasibility Analysis of Charging Infrastructure for Electric Ground Fleet in Airports

Laura Soares and Hao Wang

Many airports are converting their ground fleets to electric vehicles to reduce greenhouse gas emissions and increase airport operation sustainability. Although this paradigm shift is relevant to the environment, it is necessary to understand the economic feasibility to justify the decision. This study used life-cycle cost analysis (LCCA) to compare the economic performance of electrified ground fleets in the airport with a conventional fossil fuel fleet. Three different charging systems (plug-in charging, stationary wireless charging, and dynamic wireless charging) for pushback tractors and inter-terminal buses at a major hub airport were considered in the analysis. Although the conventional fossil fuel options present the lowest initial cost for both fleets, they cost most in a 30-year analysis period. Among three electric charging infrastructures, the plug-in charging station shows the least accumulative cost for pushback tractors, and their cost differences are negligible for inter-terminal buses. Although the electric ground fleet is proved to show economic benefits, the most cost-effective charging infrastructure may vary depending on driving mileage and system design. The use of LCCA to analyze new systems and infrastructures for decision making at the project level is highly recommended.


Performance Evaluation of Pelletized Solid Polymer Modified Asphalt Mixtures 

Danial Mirzaiyanrajeh, Christopher Decarlo, Mohamed Elshaer, Runhua Zhang, Eshan Dave, and Jo Sias

The purpose of this research is to provide a comprehensive evaluation of the effects of a solid pelletized plastomeric polymer on asphalt mixtures’ properties and performance with respect to different distresses. Five asphalt mixtures—a control mixture (no polymer); asphalt mixtures with 2.5%, 5.0%, and 7.5% polymer content; and a mixture with 5% polymer and lower asphalt binder content—were evaluated. The laboratory testing campaign included complex modulus, direct tension cyclic fatigue, semi-circular bending, disk-shaped compact tension, and asphalt pavement analyzer tests. Advanced performance-based simulation programs—MnPAVETM, FlexPAVETM, and ILLITC—were utilized to predict mixture performance in the context of pavement structure and local traffic and climatic conditions. In addition, four field test sections were constructed for all but the mixture with the reduced binder content and falling weight deflectometer (FWD) testing was conducted on the test sections. Based on the results of laboratory testing and performance simulation it can be concluded that the study modifier significantly improved the rutting performance and slightly improved the mixture fatigue performance. The study modifier did not show a considerable positive or negative effect on the thermal cracking performance. Based on the FWD results, solid polymer is potentially a good option to increase the stiffness of the asphalt concrete (AC) layer.


Competitive Effects of Joint Ventures in the International Airline Industry

Guofu Tan and Yinqi Zhang

In the past two decades, many international airline carriers have expanded their cooperation by forming various joint ventures (JVs). One key feature of these JVs is that they require carriers to determine certain airfares jointly and integrate their operations as a single carrier in the market for international air travel. This paper tries to evaluate the impact of JVs on airfares. The focus is on a set of behind-to-gateway markets between a non-gateway U.S. city and a foreign gateway city, where both online and codeshare flights are offered, to study how the airfares of online flights are affected after carriers form JVs. A new hypothesis is discussed that JVs increase the airfares of online flights. Based on this hypothesis, an empirical model is built to evaluate the Oneworld alliance’s transatlantic JV established in July 2010. This empirical analysis, which uses the U.S. Department of Transportation (U.S. DOT)’s Airline Origin and Destination Survey (DB1B) international data from 2008 to 2013, indicates that the Oneworld transatlantic JV increased airfares of online flights by about 3%–4% in the behind-to-gateway markets. Previous studies, which emphasized the airfare reductions of codeshare flights in the connecting markets, may have overestimated the benefits to consumers from JVs. U.S. DOT can better protect consumers by evaluating plausible airfare increases in online flights in the behind-to-gateway markets when reviewing new applications for JVs.


Climate-based Balanced Mix Design Method for Airport Asphalt Pavements

 Zehui Zhu and Imad L. Al-Qadi

Approximately 90% of airport runways, taxiways, and aprons in the United States are paved with 2 asphalt concrete (AC). Considering the substantial development in the commercial aircraft 3 industry and changes in pavement construction materials, the semi-performance-based AC mix 4 design method adopted by the Federal Aviation Administration requires improvement to meet 5 current and future operation needs. This paper proposes a climate-based balanced mix design 6 approach, which balances potential AC rutting and long-term cracking based on climatic 7 conditions. Performance indices used in the proposed framework include long-term flexibility 8 index, total rut depth, stripping inflection point to evaluate AC moisture susceptibility, and 9 secant modulus to assess AC stiffness. Four dense-graded airport AC mixtures at two geographic 10 locations were tested. The proposed framework appears to be effective in screening mixes that 11 may have potentially poor long-term performance, which will help build durable pavements that 12 satisfy current and future airport operation needs.


Impact of Transportation Network Companies on Ground Access to Airports: A Case Study in Austin, Texas 

Natalia Zuniga-Garcia and Randy B. Machemehl

This study proposes using intelligent transportation systems (ITS) and open-data sources to evaluate the impact of transportation network companies (TNCs) on ground access to airports. The unexpected interruption of the TNCs services in Austin, Texas, U.S., in 2016, is used as a natural experiment to provide a before-and-after analysis of the changes in the traffic conditions of the access area to the Austin-Bergstrom International Airport (ABIA). An analysis of variance (ANOVA) is implemented to determine whether the difference in speeds across periods is statistically significant, and the value of time for TNC-induced delay is estimated, using values of passengers’ willingness to pay for airport access travel time savings. Furthermore, a speed linear model is developed to assess the impact of TNC demand on ground access areas using trip information from an Austin-based TNC service. The main results suggest that airport ground access speeds were higher during the period that the TNCs were out of the city. The re-introduction of the services resulted in a speed reduction of 9% for the airport morning and 18% for the afternoon peak hours, translating to a total passenger cost of approximately $150+ (morning) and $400+ (afternoon) per hour. Furthermore, it was found that the number of TNC pick-up trips is a predictor of airport access speed and that the flight schedule can potentially be used to develop predictive speed models.