Initial telephone contact was attempted during the hours of the day and days of the week that have the greatest probability of respondent contact. The primary interviewing period was from 5:30 p.m. to 10:00 p.m. on weekdays, from 9:00 a.m. to 10:00 p.m. on Saturdays, and from 10:00 a.m. to 10:00 p.m. on Sundays (all times are local time). Since interviewing was conducted across time zones, the interviewing shift lasted until 1:00 a.m. Eastern Time (10:00 p.m. Pacific Time).
If the interview was not conducted at the time of initial contact, the interview was rescheduled at a time convenient to the respondent. Although initial contact attempts were made on evenings and weekends, daytime interviews were scheduled when necessary. If four telephone contacts on the night and weekend shifts did not elicit a household contact, the fifth contact was attempted on a weekday during the daytime.
Interviewers attempted a minimum of ten calls to each telephone number. When the household was reached, the interviewer asked to speak to an adult to screen the household for eligibility and to determine the designated respondent. When the designated respondent was reached but an interview at that time was inconvenient or inappropriate, interviewers set up appointments with respondents. When contact was made with the household, but the designated respondent was not available, interviewers probed for appropriate callback times for an appointment.
The contact protocol specified that the fifth call be made during weekdays.
Messages were left on the answering machine on the fifth, seventh and ninth
calls, if an answering machine was encountered on those attempts. The first
answering machine message explained that the household had been selected
as part of a USDOT study of American driving habits and attitudes, and asked
the respondent to call SRBI’s toll-free number to schedule an interview.
The subsequent answering messages also included the DOT website where they
could get more information about the study.