In 2006, we began a multi-year effort to evaluate the possibility of transitioning from a regularly conducted telephone survey of general public satisfaction with Oregon transportation services to either a mail-only or Web-plus-mail mixed-mode design. Two primary objectives were: 1) to identify ways to counter the trend toward lower telephone survey response rates and 2) to evaluate the impact of alternative designs on data quality.
Three experiments were conducted for which unit response rates analyses have been reported elsewhere (Lesser and Newton, 2007; Lesser et al., 2011a; Lesser et al., 2011b). In this study, we consider whether switching from telephone to mail or a combination of mail and Web will have a deleterious effect on item nonresponse, as previous research has suggested (e.g., de Leeuw et al., 2003).  
Thus, our purpose is to examine overall item nonresponse rates for each of the individual modes and mode combinations. Implications for replacing telephone by these alternatives are also discussed.