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Airport managers and planners require a wide range of information to support their plan- ning activities and decision making. While some of the information needed for effective planning and management of airports can be obtained by direct observation or from statis- tics that are routinely collected, much cannot. Some airport user attributes are not directly observable and some statistics are not routinely collected. Airport user surveys are the only way to obtain information of this type, examples of which include air passenger character- istics, customer satisfaction with airport facilities and services, ground access trip origins, and use of ground transportation modes. This guidebook has been developed to help airports and other survey sponsors plan, design, conduct, and analyze surveys of airport users. It is intended to improve understanding of the issues involved in planning and implementing such surveys and to provide practicable meth- ods and techniques to overcome these issues. There are a number of different categories of airport user, and surveys of a particular category of user involve issues common to all surveys as well as issues specific to that type of airport user survey. The guidebook first addresses those issues that are common to all airport user surveys. These sections are followed by a sequence of chapters that address issues that are specific to the following categories of airport user: ⢠Air passengers ⢠Airport-based employees ⢠Airport tenants ⢠Area residents ⢠Area businesses ⢠Air cargo activities Planning a Survey Thorough planning is absolutely essential to the success of any survey effort. Unfortunately, this task is often allotted insufficient time and attention, resulting in inaccurate or inadequate data. The first steps in planning any survey is to clearly define the purpose of the survey and then to decide who should be involved in the planning process. These steps will lead to the for- mation of two distinct teams. The survey planning team will be responsible for the planning, design, and overall conduct of the survey, as well as reporting the results. The survey imple- mentation team will comprise the interviewers, supervisors, and support personnel who will actually perform the survey. Some of the members of the survey implementation team will also serve on the survey planning team. A key step in planning a survey is choosing the appropriate survey method. The principal survey methods comprise intercept surveys using interviews or self-completed questionnaires, 1 S U M M A R Y Guidebook for Conducting Airport User Surveys
mail or telephone surveys, or World Wide Webâbased (Internet) surveys in which respon- dents complete the questionnaire online. Intercept surveys are the only practical method for air passenger surveys. A second major consideration is when to perform the survey and whether the survey should be performed over several different periods to account for sea- sonal variation in airport user characteristics. Decisions will be needed on where to perform the survey and whether it will be necessary to contract out all or part of the work. If the sur- vey is to be performed in the secure area of the airport, it will be necessary to obtain security clearance and identification badges for the survey personnel who do not already have these; this need will affect the staffing requirements and schedule. At this point, it will be possible to prepare a detailed budget and establish a preliminary schedule and target dates. Statistical Concepts The third chapter of the guidebook is intended to provide the non-statistician with an understanding of the basic statistical principles behind sample design, the terminology involved, and the importance of considering how the sampling approach and the sample size interact to determine the statistical accuracy of the resulting data. Although it is not unusual to present the results of airport user surveys without any real discussion of the likely accuracy of those results, such presentation is not good practice. The proper approach to planning any survey is first to decide how accurate the results need to be and then to design the survey accordingly, as well as ensure that decision makers using the survey results are aware of the likely accuracy of the results. One of the most fundamental questions in planning a survey is deciding how large a sample size is required, because sample size has a major influence on both the cost of conducting the survey and the accuracy of the results. The required sample size is in turn influenced by the sampling approach adopted. The most straightforward approach to obtaining a repre- sentative sample from a population is to select the members of the sample randomly from among the members of the population. However, in practice random selection is often difficult to achieve, particularly in an airport environment. Furthermore, it has the disadvantage that the sample will include relatively few members of particular subgroups of the population that com- pose only a small proportion of the total population. To address these concerns, other sampling methods that are often used include sequential sampling, stratified sampling, and cluster sam- pling. The chapter discusses the difference between these approaches and shows how for each approach the sample size required to achieve a given level of accuracy can be determined. Survey Design Many aspects of designing an airport user survey are common to all types of survey. These aspects include defining the population of interest to be surveyed, developing a sampling strategy and sampling plan, and addressing issues involving the design and wording of the survey questionnaire. Consideration needs to be given to ways to maximize response rates, including explaining the purpose of the survey to potential respondents and having field staff wear identification badges and distinctive attire that indicates that the survey is an officially sanctioned activity. In some cases it may be desirable to translate the survey questionnaire and supporting materials into other languages, although the choice of which languages to use is often problematic. The increasing use of electronic data collection devices for performing survey interviews presents both opportunities and technical and logistical constraints. They can support much 2 Guidebook for Conducting Airport User Surveys
more complex survey questionnaires and eliminate the need for a separate data entry step. They can also be programmed to perform real-time data checking. However, consideration needs to be given to who will do the necessary programming. Commercial software packages are available and the choice of the most appropriate package will usually involve a tradeoff between cost and required features, as well as compatibility with the chosen equipment. The choice of equipment also involves tradeoffs between cost, capability, and ease of use. Such factors as screen size and clarity, data storage capability, key size and keypad layout, battery life and recharge time, data export capability, and weight and handling will influence both cost and usability. Other steps in survey planning include interviewer selection and training, testing of the questionnaire and survey procedures, arrangements for data entry and quality control, analy- sis and reporting of survey results, post-survey analysis and identification of any lessons learned for use in future surveys, and documentation of the entire survey process for future reference. Where survey responses are recorded on paper forms, it will be necessary to enter the data into a computer file and verify that the data has been entered correctly. Although the use of electronic data collection devices will eliminate much of the data entry and verification task, the data will still need to be checked for consistency and any obvious or apparent errors made in entering the survey responses. Identifying and correcting errors in the response data can be a very time-consuming task, but essential to the quality of the resulting information. Air Passenger Surveys Air passenger surveys are the most common type of airport user survey, but they involve many complex issues that need careful consideration if the results are to be useful and accurate. The more important issues include whether to interview passengers or use self- completed questionnaires, where to perform the survey, when to perform the survey and for how long, and how large a sample size is required. Development of an appropriate sam- pling plan and development of a well-designed and carefully worded questionnaire are major factors that influence the accuracy and usefulness of the survey results. Because air passenger characteristics vary by time of day and day of the week, the sampling plan should cover all the hours of the day and at least a complete week. Even so, the survey responses are unlikely to completely match the distribution of air passengers over the week and across dif- ferent market segments; therefore, the survey responses will need to be weighted to obtain an accurate profile of passenger characteristics at the airport. The choice between self-completed questionnaires and interviews involves a balancing of cost and desired accuracy. Self-completed questionnaires generally cost less per response, thus allowing a larger sample size for a given budget. However, there is no opportunity to clarify questionable responses, ensure that all relevant questions have been answered, or tailor questions in the light of answers given to previous questions. Where self-completed questionnaires involve open-ended questions, such as trip origin addresses, there may also be a problem interpreting handwriting. The use of electronic data collection devices for interview surveys facilitates tailoring questions to previous responses and more complex skip patterns than is usually possible with printed forms. With suitable programming, they can also perform real-time validity and consistency checks of respondent answers, and prompt the interviewer to probe for clarification of questionable responses. This capability is par- ticularly valuable for air passenger surveys, where many respondents may use incorrect or ambiguous terminology in their answers, or misunderstand the question. While the majority of air passenger surveys are performed in the airline gate lounges, this location presents a number of potential sources of bias in the survey results. The most Summary 3
obvious is that responses are usually limited to passengers in the market served by the next flight departing from the gate where the survey is performed, but other sources of potential bias arise from the fact that passengers are arriving in the gate lounge as the survey is being performed and passengers arriving just before or after boarding begins are unlikely to be sur- veyed. An alternative approach is to intercept passengers as they exit security screening. This approach allows a reasonably random sample of originating passengers, although passengers clearing security shortly before their flight is due to board will not have time to complete the survey. However, this location is likely to miss most or all of the connecting passengers. Air passenger characteristics vary seasonally as well as by time of day and day of the week. Therefore any survey performed over a relatively short period of time will necessarily not reflect this seasonal variation. Depending on the use to which the survey results will be put, it may be desirable to perform the survey in several waves at different times of the year. Alternatively, a continuous or quasi-continuous survey could be performed on an ongoing basis throughout the year. Use of such a survey period would not only provide information on how air passenger characteristics vary seasonally, but also require fewer survey field staff for a given sample size, simplifying the logistics of performing the survey and allowing the field staff to be better trained and become more experienced in conducting the survey. The sequence and wording of air passenger survey questions can significantly affect the reli- ability of the responses that are obtained. Particular care is needed to word questions in a way that will be understood by the traveling public. Local terminology for different ground access modes varies widely across the country, and may mean a very different thing to a visitor from another region or country than to a local resident. The sequence of questions can also affect how respondents interpret them, either positively by introducing questions in a logical sequence that helps respondents interpret the question correctly, or negatively by creating potential ambiguities over which aspect of the trip a question is addressing. Performing an air passenger survey involves a large number of logistical details that need to be carefully planned. If the survey is being performed in the secure area of the terminal, as is usually the case, the survey field staff must be issued security badges. This process can take a significant amount of time to complete and some potential field staff may be rejected by the required background check. Other considerations include arranging for the use of a field office where equipment and supplies can be stored, and data downloaded from electronic data collection devices if these are used, as well as arrangements for pre-testing the survey ques- tionnaire, selecting and training field staff, and performing pilot tests to identify potential problems with the survey logistics. Groundside surveys of vehicle occupants form a special type of air passenger survey that can be used to obtain detailed information for planning airport groundside facilities. These surveys can provide detailed information on vehicles, greeters, and well-wishers as well as passengers and are performed at various locations on the airport landside, including termi- nal curbs, parking facilities, and shuttle bus or public transportation pick-up and drop-off stops. Because the sampling rate varies widely from location to location and time to time, the results need to be weighted using counts of vehicles at different facilities as well as counts of originating and terminating air passengers. Employee Surveys Surveys of airport-based employees are conducted for a variety of reasons, including assessing satisfaction with facilities and services, obtaining information for transportation or concession planning, or addressing employee-related issues such as communication and 4 Guidebook for Conducting Airport User Surveys
knowledge of airport procedures. Two approaches can be used: developing a list of all employees on which to base the survey or conducting intercept surveys at suitable loca- tions on the airport. Questionnaires can be distributed to the selected sample of employees by mail or distributed by employers, and responses can be returned by mail or at drop boxes in break rooms or other suitable locations. Alternatively, employees can be contacted by email or mail and invited to participate in a Web-based survey. Questionnaires are usually self-completed, but an on-site intercept survey could collect responses through interviews. The time needed to complete the survey should be no more than 5 to 10 minutes if employees are expected to complete the survey during a break. Tenant Surveys Surveys of airport tenants are usually conducted to collect information for studies of the economic impact of airports or to determine tenant satisfaction with the airport as landlord. The best method for conducting these types of surveys is to send invitations to participate by email with a link to a Web-based survey. These surveys should be conducted by respected third parties and provide assurances that the responses will remain confidential. âMystery shopperâ surveys form a different type of tenant survey. These surveys collect detailed infor- mation on the performance of airport concessions by having survey staff make anonymous purchase and return transactions and subsequently complete an assessment questionnaire that evaluates the quality of the customer service and other attributes of the concessions. Surveys of Area Residents Most surveys of area residents are conducted to obtain information for marketing and airport planning purposes, particularly studies that explore the use of different airports by local residents in situations where they have a choice of airport. These surveys are typically performed by telephone using random-digit dialing, although this method presents a num- ber of potential sources of bias, including unwillingness of those called to participate in the survey, households without telephones or only cellular phones, and numbers that are not answered after repeated calls. To minimize the rate of incomplete surveys, the survey should be kept to no more than 10 minutes. Surveys of Area Businesses Surveys of area businesses and other organizations are undertaken for a number of rea- sons, including collecting information for use in economic impact studies and collecting information on the air travel needs of local businesses and their travel characteristics. Various methods can be used for such surveys, including mail surveys, telephone surveys, in-person interviews, and Web-based surveys with an initial contact by email. Defining an appropriate sample of organizations to contact to request participation in the survey and assembling the appropriate contact information in each case can require a significant level of effort. Questionnaires should be kept as short as possible, consistent with the goals of the survey, to maximize response rates. Particular thought should be given to how to handle local branches of larger organizations. Care also should be taken in word- ing questions to determine whether any reasons or opinions provided by respondents are those of the person responding to the survey or represent the position of the organization as a whole. Summary 5
Cargo Surveys Surveys of air cargo activities and operations at an airport represent a particularly challeng- ing type of survey, because information on shipment characteristics and detailed cargo flows is typically regarded as highly proprietary. Because the cargo itself cannot be surveyed, the organizations involved in handling the cargo must be surveyed. While some information may be obtained from truck surveys, truck drivers are generally reluctant to spend much time answering detailed questions or may not feel authorized to reveal information about the ship- ments they are transporting. In spite of these difficulties, cargo surveys provide an important addition to the information that can be obtained from cargo traffic statistics that are routinely reported, which typically only provide very aggregate measures of the weight of cargo moved and little to no information about the commodity type, weight, value, density, and the origin and destination of individual shipments. Surveys of air cargo carriers, freight forwarders, or selected shippers will typically take the form of an in-person interview. Respondents may be able to provide useful information in general terms, even if they are not willing to provide detailed data on individual shipments. The advent of automated truck-tracking capabilities through the introduction of Intelligent Transportation Systems programs and weigh-in-motion systems at truck inspection stations may provide useful information in certain corridors that can be combined with other survey data to better understand air cargo flows, although this aspect is not well understood and could benefit from future research. 6 Guidebook for Conducting Airport User Surveys
