1995 American Travel Survey (ATS)

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1995 INTRODUCTION growing industrial sectors in the United States. In many areas of the country, travel-related services The Intermodal Surface Transportation Efficiency form the primary industries for providing income AMERICAN Act of 1991 (ISTEA) created the Bureau of Transpor- and jobs for many of its residents. In view of the im- tation Statistics (BTS) in the Department of Trans- portance of travel and transportation to the eco- TRAVEL portation (DOT). In December of 1992, the BTS was nomic and social well-being of America, formally established to compile, analyze and pub- comprehensive and timely data relating to this sec- SURVEY lish statistics; to develop a long-term data collection tor are essential to government, private industry, program; to develop guidelines to improve the cred- and others responsible for policy formation and pro- ibility and effectiveness of the DOT’s statistics; to rep- AN OVERVIEW OF THE SURVEY motional activities in the general field of travel and resent transportation interests in the statistical DESIGN AND METHODOLOGY tourism. community; and to make statistics accessible and The main objective of the ATS is to provide policy understandable. At about the same time, the Trans- makers with more accurate and comprehensive in- portation Research Board of the National Academy formation than has previously been available about of Sciences in its report, Data for Decisions: Re- the travel of persons and households in the United quirements for National Transportation Policy States and about the principal characteristics of Making, concluded that the biggest gap in the DOT’s travel and travelers. The survey will provide key data intermodal data program was in “flow data.” The most recent source of data on passenger flows dates back to the 1977 National Travel Survey, conducted by the Bureau of the Census as a component of the quinquennial Census of Transportation. To meet the need for passenger flow data, the BTS conducted the 1995 American Travel Survey (ATS). The ATS field work was performed by the Census Bu- reau, under its authority to conduct a Census of Transportation as stated in Title 13 of the U.S. Code. In the future, BTS plans to conduct the survey every five years. This paper describes the methods used in the to assist in the formulation and evaluation of initia- 1995 ATS. The introduction provides an overview of tives in intermodal transportation. Because policy- the purpose and objectives of the survey followed by makers have a particular interest in understanding a description of the survey and sample designs, sur- the differences in travel patterns by state, the ATS will vey field operations, and processing of survey data. provide detailed information on state-to-state travel The intention of this paper is to provide a reference as well as travel to and from metropolitan areas by to data users that will aid in the analysis of the data mode of transportation. Data will also be available when they become available. for subgroups defined in terms of characteristics related to travel, such as business, vacation or com- A. SURVEY OBJECTIVES bined/business pleasure travel by age, family type, labor force status and income. Subgroups of special The American Travel Survey was designed to ob- interest may include, for example, frequent travel- tain information about long-distance travel of per- ers, trips taken by children traveling without a par- sons living in the United States. The information is ent, and trips taken by retirees. needed to identify characteristics of current use of To achieve survey objectives, both cross-sectional the nation’s transportation system, forecast future and longitudinal estimates were needed. Key cross- demand, analyze alternatives for investment in and sectional estimates include the origins and destina- development of the system, and assess the effects of tions of trips, the proportions of people traveling on Federal legislation and Federal and state regulations various transportation modes, intermodal connec- Susan J. Lapham on the transportation system and its use. tions, reasons for trips, trip duration, trip distance, Bureau of Transportation Economic activity generated from people travel- Statistics, U.S. Department and person and household characteristics that may of Transportation ing represents one of the largest and most rapidly influence aggregate travel deman during a particu-

1995 AMERICAN TRAVEL SURVEY An Overview of the Survey Design and Methodology 1 lar time period. Longitudinal estimates require the ever, information about trips taken up until the collection of information about travel behavior or time a respondent became ineligible was collected. the members of households and persons over the en- Persons who moved into the original sample address tire survey year. For example, it may be desired to after the initial interview were interviewed and a se- measure the cumulative effect of patterns of travel ries of brief questions was asked about all trips taken on the transportation system or the patterns of since January 1, 1995. This retrospective travel in- change in travel by season. formation was used to make weighting adjustments in the annual estimates. Households not interviewed for any reason during B. SURVEY AND SAMPLE DESIGN a particular interview period were contacted and in- 1. Survey Design terviewed at a subsequent time and asked about travel taken during the missed travel quarter. Be- ATS uses a quinquennial design, collecting data cause the recall period was longer for these few re- for calendar years ending in zero and five. A sample spondents, trip information was limited to the of households was selected at the beginning of cal- number of trips, mode of transportation for each endar year 1995. Interviewing of households in the trip, primary purpose of each trip, and the origin 1995 survey, which contained about 80,000 eligible and destination of each trip. Again, the retrospective addresses, began in April 1995 and ended in March 1996. Sample households were interviewed four times during this period, at approximately three- month intervals. The survey was based on a probability sample of households from each of the 50 states and the Dis- trict of Columbia. The survey population for ATS consisted of persons resident in households and persons living in group quarters, such as dormitories, rooming houses, religious groups dwellings, and family-type housing on military bases. Persons living in military barracks and in institutions, such as prisons and nursing homes, were excluded. information on these trips are used only to make adjustments in annual data. 2. Sample Design C. QUESTIONNAIRE CONTENT Sample selection for ATS was based on lists of addresses compiled by the Census Bureau from the de- Basic demographic characteristics and other cennial censuses of population. In addition to the classification variables associated with a household ATS, the Census Bureau uses address-based lists to and its members were recorded during the initial in- provide samples for all of its major household sur- terviews for the survey and were updated or verified veys, including the Current Population Survey, Na- in each subsequent interview. Social and economic tional Crime Survey, and the American Housing characteristics included age, sex, marital status, Survey. race, household type, Hispanic origin, education, la- After the sample of addresses was selected for the bor force status, and income. Detailed information ATS, rules were established to determine which per- about each trip taken by each member of the house- sons should be included in initial interviews at those hold was collected quarterly. The main trip charac- sample addresses. At the initial interview, all persons teristics included the purpose of trip, means of whose usual residence was the sample address were transportation, origin, destination, intermediate included and remained in sample as long as they stops, travel dates, trip duration, number of nights remained at the sample address. Persons who left away, and types of lodging used. Travel distances for the survey population through death, going abroad, each trip were assigned based on transportation net- or changing residence to another address were con- work routing algorithms. sidered ineligible for subsequent interviews. How-

1995 AMERICAN TRAVEL SURVEY An Overview of the Survey Design and Methodology 2 Household-level questions were asked only once the start of the first interview, the interviewer re- for each household and were updated if necessary corded the basic demographic characteristics for throughout the survey year. The detailed trip ques- each person residing at the sample address, plus a tions were asked of the initial respondent. If this re- few characteristics of the household and the hous- spondent was knowledgeable about other household ing unit. The telephone number and address were members’ travels, he or she served as a proxy re- verified and recorded in case callbacks were needed spondent for other household member’s trips. Oth- to obtain additional information. The interview was erwise, the individual household member was conducted on a trip-by-trip and person-by-person contacted and interviewed. Trip characteristics were basis until the questionnaire was completed for all asked about each trip reported by the respondent for trips taken by each household member. each member of the household. Other instruments used in the data collection process were a series of advance letters and one phone call. These include a prenotice letter, survey package D. DATA COLLECTION PROCEDURES (letter, calendar/diary, and map), introductory tele- Interviews were conducted by Census Bureau field phone call, post cards to remind household mem- staff under the supervision of the Census Bureau’s bers to continue to keep track of their travel 12 permanent regional offices and by interviewers information, and reminder letters. working under the supervision of the Census The prenotice Bureau’s three centralized telephone facilities. Most letter served as a interviews were by telephone, either by field repre- notice to the re- sentatives working with laptops from their homes or spondent that the by interviewers working with personal computers household was se- from centralized telephone facilities. Personal visit lected for the sur- followups were used to obtain missing information vey and provided for non-responding households. Completed inter- general informa- views were transmitted electronically to Census Bu- tion about the sur- reau headquarters from the field representatives’ vey. The letters homes and from the centralized telephone facilities carried the signa- on a daily basis. tures of the Secre- tary of Commerce and the Secretary of 1. Basic Data Collection Features Transportation. The survey package included a sec- ond letter containing more detail about the ATS with The length of a household interview depended in answers to some commonly asked questions. A travel part on the number of trips taken by the household calendar was included in the survey package. The members. The length of each quarterly interview for calendar contained instructions on how to record all households averaged 12 minutes. Interviews travel information and space to record the details of ranged from a low of 3 minutes to a high of just travel taken during the travel period. The calendar over two hours. Any person aged 18 and over who was used as a recall aid and was not collected from was present at the time of the interview could report the respondent. for themselves and other household members unless After the survey package was mailed to sample not physically or mentally able to do so. Proxy re- households, a phone call was made to each house- sponses were accepted for persons as long as the re- hold to describe the importance of the survey, to en- spondent was knowledgeable about the other courage participation, to explain what the household members’ travels. Information for chil- respondents needed to do, and to answer questions. dren was collected from a knowledgeable adult. This phone call also served as a bounding technique to help the respondent recall travel taken since the 2. Data Collection Instruments telephone call. Reminder post cards were sent about half way through the three month travel period to The primary data collection instrument for the remind respondents to fill in the calendar/diary if ATS was an electronic questionnaire programmed and/or when they travel. About four weeks prior to for the computer in the CASES software language. At each subsequent interview, reminder letters were

1995 AMERICAN TRAVEL SURVEY An Overview of the Survey Design and Methodology 3 sent to each household to remind the respondents to based on the transportation network depend on expect a phone call from an interviewer. mode of transportation, and information about stops made along the way. 3. Data Collection Strategies 4. Interviewer Characteristics, Training Several broad strategies were adopted in design- and Supervision ing the data collection instrument and the interview process. Travel information was collected in chrono- a). Interviewer characteristics logical order from the beginning of the reference pe- In April 1995, approximately 1,200 interviewers riod (longer ago in time) to the time of the were hired and trained to work on the ATS. A large interview. In addition, for each trip reported, the majority of the interviewers were women. The aver- question items were sequenced in roughly chrono- age monthly workload for the ATS was about 14,000 logical order. For example, after the main destina- households. Interviewers typically completed most of tion and dates of a trip were obtained, the their interviews during the first two weeks of each respondent was asked to report the mode of trans- month of interviewing. Interviewers were paid on an portation, reason for the trip, travel partners, stops hourly basis, receiving between $8.00 and $12.00 along the way to the main destination, type of lodg- per hour. ing at the main destination, overnight side trips taken while staying at the main destination, and b). Interviewer training stops on the way home. Training for ATS interviewers included home Since some trips are taken by more than one study, classroom training, on-the-job training and member of the household, information was col- refresher training. Interviewers new to ATS received lected about all trips taken by the respondent first. intensive training, including four hours of self-study Next, questions were asked about trips taken by and four days of classroom training as well as an other household members, excluding trips already additional six hours on listing operations. Training reported in order to avoid collecting redundant trips. sessions included lectures, audio-visual presenta- The use of records, such as the calendar provided in tions, mock-interviews, and classroom discussion. the survey package, a personal calendar, receipts Trainees received detailed information about their from airlines, trains, buses, hotels, etc., may have jobs, the concepts and definitions used in the travel helped respondents to provide more accurate infor- survey, and specific interviewing techniques. As part mation. The use of a calendar and map was espe- of the initial training, each interviewer practiced cially helpful in completing the detailed trip several interviews. Interviewers received training on information. Interviewers were instructed to encour- new information and on special aspects of the sur- age respondents to take time to get their calendar or vey as needed during the survey period. Interviewers records for reference during the interview. In addi- found to be weak in certain aspects of the survey re- tion, interviewers were provided with a United States ceived supplemental training to help them meet re- atlas for their own reference during the interview. sponse rate and accuracy standards. The measurement of trip mileage in the ATS was an important factor for at least two reasons: 1) to c). Supervision and quality assurance determine whether the distance traveled was The work of the interviewers was monitored, and sufficient to meet the 100 mile trip definition, (al- feed back was provided in several ways. The work of though ATS asks respondents to provide information each experienced interviewer was observed by a su- on all trips of 75 miles or more, published data will pervisor who checked the interviewer’s performance include information only for those trips of 100 miles in establishing rapport with the respondents, asking or more); and 2) to get an estimate of total miles questions in an appropriate manner, probing, and traveled from origin to destination and return. The recording answers accurately. The results of the ob- method of calculating trip and trip segment mileage servations were discussed with the interviewers and consisted of computerized algorithms designed to interviewers whose performance was below standard estimate both great circle and transportation net- had their work observed more often. work distances using the respondent’s reported ori- A systematic reinterview program served the dual gin and destination place names. Mileage estimates purposes of checking a sample of the work of the in-

1995 AMERICAN TRAVEL SURVEY An Overview of the Survey Design and Methodology 4 dividual interviewers and identifying aspects of the 1994 ‘SF-83, Request for OMB Review,’ internal field procedures which may need improvement. The Census Bureau supporting statement issued with quality assurance reinterview sample covered about OMB package, October 3. five percent of each interviewer’s work each month. 1994: ‘Sampling Specifications for the 1995 The reinterviews, which were completed as soon as American Travel Survey,’ internal Census Bureau possible after the original interview, were conducted memoranda for Demographic Surveys Division from on the telephone by a supervisor. The reinterviews Demographic Statistical Methods Division. were used to determine whether the interviewers 1994: ‘Suggestions for American Travel Survey,’ conducted the interview at the correct address, internal Census Bureau memoranda for Demo- classified noninterviews correctly and determined graphic Surveys Division from Don Dillman, June household composition correctly. Several trip ques- 28. tions were also checked to verify that the interviewer 1994: ‘Request for Cost Estimate for American asked these items during the original interview. The Travel Survey—Project 7109,’ internal Census Bu- results of the reinterview were used to take corrective reau memoranda for Thomas Meerholz and Barry action, such as supplemental training or termina- Fink, June 2. tion. 1979: ‘Travel During 1977,’ National Travel Sur- vey, 1977 Census of Transportation, TC&&-N-2, Washington, DC. E. PRODUCT PLANS

The data products from the 1995 ATS will provide Federal Highway Administration national estimates, information on travel within 1992: ‘National Intercity/Intercounty Travel Sur- and between census regions and divisions, informa- vey Scoping Analysis: Final Report,’ internal report tion on state-to-state passenger travel, and travel to prepared by Science Applications International Cor- and from metropolitan areas. BTS will release the poration, Cambridge Systems, and Peat Marwick. ﬁrst ATS data products beginning in the summer of 1991: ‘National Personal Transportation Survey: 1997. Public-use data tapes will be available on CD- Users Guide,’ US Department of Transportation, ROM. Paper products will likely include reports Washington, DC. showing household, person, and travel characteristics, travel proﬁles, and a chart book, among others. US Travel Data Center All ATS products will be available on the Internet. 1994: ‘1993 Travel Market Report: Full Year Re- sults from the National Travel Survey,’ Travel In- dustry Association of America, Washington, DC. F. CONCLUSION 1993: ‘1992 Travel Market Report: Full Year Re- To obtain more information about the American sults from the National Travel Survey,’ Travel In- Travel Survey and its status, contact Susan J. dustry Association of America, Washington, DC. Lapham, BTS Transportation Surveys and Program Manager, at 202 366-9913 or by e-mail at [email protected].

REFERENCES Bureau of the Census 1994 ‘Results of CATI and RO Interviewing for the Pretest for the American Travel Survey,’ internal Census Bureau memoranda for the record, Decem- ber 28.

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