Research Projects

Air Passenger Values of Time and Qualitative Travel Attributes

Assigned to Geoffrey Gosling
Last Edited by Geoffrey Gosling

The proposed research will update and extend the estimated values of travel time savings determined in prior ACRP research and broaden the scope to include not only travel time savings but also other quantitative service attributes, such as walking distance, and the perceived values attributed by air passengers to qualitative levels of service, such as ride quality and comfort. The research will also explore the importance of travel time variability relative to changes in the average travel time, as well as how air passengers make allowances for travel time variability and delays in their trip planning.

Background (Describe the current situation or problem in the industry, and how your idea would address it.)

The implied values that air passengers attribute to travel time, walking distances, and qualitative travel attributes such as ride quality, comfort, and convenience can have a significant influence on their use of ground transportation or internal airport circulation modes. This travel behavior in turn influences the design of airport ground access mode choice and airport choice models, as well as such issues as the fares and rates to charge for airport ground transportation or other airport services. Even where no fare is charged directly, the benefits that air travelers derive from reduced travel time or improved level of service can form a major component of benefit-cost analysis used to justify airport development projects.

A recent ACRP project (03-19) documented in ACRP Web-Only Document 22 Passenger Value of Time, Benefit-Cost Analysis, and Airport Capital Investment Decisions developed estimates of air passenger values of time for different components of the journey from trip origin to destination, including airport ground access, time spent in various activities within the airport passenger terminal, including security screening and waiting at the gate, and time spent flying to the destination, including any flight delays. These estimates were derived from a set of stated preference choice experiments conducted as part of a web-based survey of household members who had taken a domestic air trip in the past six months. This research is believed to be the first attempt to estimate values of travel time for different segments of an air journey within the airport and there has been no further research into these issues since the results of the research were published beyond some work that has generated estimates of average values of time for airport ground access trips. However, the previous research did not address how such quantitative service attributes as the walking distances involved in the various trip segments or qualitative service attributes such as comfort or reliability influenced the perceived value of travel time.

Furthermore, the survey on which the findings of ACRP Project 03-19 were based had a sample size of about 1,170 respondents due to project budget constraints (the survey was only one part of a more broadly scoped project). Although adequate for the analysis undertaken for the project, this limited the ability to explore differences in the values of time for different subsets of the air traveler population, since those subsets would have had too small a sample size for statistically significant estimates of the implied values of time. It was also decided to separate the choice experiments into two different sets of stated preference experiments to avoid presenting the survey respondents with an excessively complex set of choice alternatives. One set of experiments examined different alternatives for the flight from the origin to the destination airport while the other examined different alternatives for the components of the trip from the ground origin to the airport departure gate. A consequence of this experimental design is that it is unclear whether the estimated values of time for different components of the flight (flight time, time making an intermediate connection, and any delays) are consistent with the estimated values of time for the ground access and airport terminal components of trip, since these came from different stated preference experiments. The experimental design also provided no opportunity to estimate perceived values of qualitative level of service attributes, since this would have unduly complicated the choices faced by survey respondents and the sample size did not allow different attributes to be addressed in separate choice experiments.

By utilizing a considerably larger sample survey, the proposed research would add significantly to the findings of ACRP Project 03-19 by allowing estimates of travel time savings for different subsets of the air traveler population, accounting for quantitative and qualitative travel attributes that were not addressed in the prior research, and allowing the estimated values of travel time savings to be better tailored to the specific conditions at a given airport. To the extent that changes in technology, such as self-ticketing, biometric screening, and provision of information directly to travelers via smartphones, affect their perceived values of time, these effects can be considered in the proposed research. In addition, the research will provide some indication of how the perceived values of travel time savings have changed in the eight or so years since the survey undertaken for ACRP Project 03-19 was performed.

Since almost all airports undertake some form of benefit-cost analysis of planned projects (or at least consider both the benefits and costs of planned projects if only in an informal way), the results of the proposed research will be widely applicable and the ability to tailor assumed values of time used in benefit analysis to local circumstances should enhance the validity of the analysis. At the same time, more granular estimates of air passenger values of travel time savings will improve the accuracy of any analysis, potentially affecting the conclusions drawn regarding the economic justification of specific projects.

A better understanding of how quantitative and qualitative travel attributes affect air passengers perceived values of time will be particularly helpful in assessing airport ground access/egress mode choice in the current rapidly changing environment resulting from ride-hail and other new services, as well as the assessment of terminal improvement projects that commonly need to balance the space allocated to concessions with the need to maintain operational efficiency and avoid excessive walking distances within the terminal.

Objective (What is the desired product or result that will help the airport industry?)

The objective of the proposed research is to update and extend the estimated values of travel time savings determined in ACRP Project 03-19 and broaden the scope to include not only travel time savings but also other quantitative service attributes, such as walking distance, and the perceived values attributed by air passengers to improvements in qualitative levels of service, such as ride quality and comfort. One important objective of the research is to explore the importance of travel time variability relative to changes in the average travel time, as well as to better understand how air passengers make allowances for variability in travel times and delays in their trip planning. Improved understanding of air passenger values of travel time savings and other service attributes will benefit airports through more detailed benefit-cost analysis of capital investment decisions and assessment of factors to be considered in operational decisions.

Approach (Describe in general terms the steps you think are needed to achieve the objective.)

The proposed approach to the research would be based on the design and conduct of a much larger sample web-based survey or other experimental approach that would allow more complex choice experiments by segmenting the choice alternatives in different ways in order to explore different aspects in subsets of the overall sample. As was done in the survey conducted as part of ACRP Project 03-19, this web-based survey or other approach would collect detailed household characteristics as well as details of the most recent air trip undertaken by the survey respondents or study participants and their air travel frequency over the prior year. These survey or study results would provide a large-sample profile of air travel characteristics at a national level, something that has not been done since the 2001/2002 National Household Travel Survey.

In order to broaden the pool of survey respondents to ensure that they provide a representative sample of the air traveling public, consideration should be given to pre-screening survey participants from commercially available Internet survey panels or supplementing the use of such panels by recruiting additional survey participants from segments of the flying public who may be underrepresented in or missing entirely from Internet survey panels, such as elite members of airline frequent flier programs or frequent business travelers.

The larger survey sample size or number of study participants compared to the previous research would allow greater segmentation of the survey respondents or study participants and the use of different stated preference experiments to explore values of travel time in additional segments of the total air trip, such as time spent at the destination airport compared to the origin airport or time spent on the return trip compared to the outbound trip, without requiring an unreasonably lengthy survey.

The proposed research would consist of the following tasks:

Phase I

Task 1 Literature review – Update the literature review undertaken as part of ACRP Project 03-19 to address subsequent literature.

Task 2 Experimental design – Identify the issues to be addressed in the web-based survey or other experimental approach, prepare an experimental design to define the choice experiments to be performed, and specify the alternatives to be used in the choice experiments.

Task 3 Survey design – Prepare a draft survey or other experimental instrument, review with Project Panel and revise to address comments and suggestions, and implement prototype survey or experimental approach.

Task 4 Test survey or experimental methodology – Perform a pilot survey or experiments to test the survey instrument or experimental approach and experimental design.

Task 5 Interim Report - Prepare and submit draft Interim Report and meet with Project Panel to review Phase I results and plans for Phase II.

Phase II

Task 6 Recruit participants for the web-based survey or other experimental approach.

Task 7 Conduct the survey or other experimental approach.

Task 8 Analyze the results of the survey or other approach addressing the previous air travel by survey respondents or study participants and the relationship with respondent or participant household characteristics.

Task 9 Analyze the results of the survey or other approach to determine how representative the survey respondents or study participants are to the national air travel population.

Task 10 Estimate choice models from the results of the survey or other choice experiments and determine implied values of time, reliability, walking distance, and qualitative level of service attributes.

Task 11 Final Report – Prepare draft Final Report documenting the project findings, submit for Project Panel review, revise to address comments and concerns, and coordinate with ACRP staff to publish final version.

Cost Estimate and Backup (Provide a cost estimate and support for how you arrived at the estimate.)

It is estimated that 14 person-months of effort would be required to undertake the proposed tasks. Together with costs for travel and data acquisition, the funding required for the research is estimated at $495,000. This includes $80,000 for Internet survey panel costs and $9,000 for travel and other direct expenses.

The level of effort is based on assigning person-months of effort to each of the above tasks and an average cost of $29,000 per person-month based on the budgeted cost for recent ACRP projects.

It is envisaged that the proposed research could be conducted over a period of approximately 24 months, including allowances for Project Panel review of draft intermediate and final deliverables.

Related Research - List related ACRP and other industry research; describe gaps (see link to Research Roadmaps above), and describe how your idea would address these gaps. This is a critical element of a synthesis topic submission.

In addition to the research undertaken for ACRP Project 03-19 and the prior research documented in the literature review performed as part of that project, there have been a number of subsequent studies that have addressed air traveler values of time directly or indirectly through airport ground access mode choice or airport choice models. Two such papers were presented at the 2017 TRB Annual Meeting: Karina Hermawan and Amelia Regan, "On-Demand, App-Based Ride Services: An Emerging Ground Transportation Mode at Los Angeles International Airport" (Paper 17-01061); and Duncan Kisia, "Understanding Issues in Airport Ground Access Modeling: Lessons from a Revealed Preference Study of New York Metropolitan Area Airports" (Paper 17-06882). Both papers developed airport ground access mode choice models that allow the calculation of implied values of air traveler ground access time. In particular, the paper by Duncan Kisia includes a fairly detailed analysis of how household income influences perceived values of ground access travel time.

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