Self-report approaches include questionnaires, interviews, focus groups and driver diaries. They are relatively inexpensive, provide detailed information and can reach large numbers of people. However, it is unclear to what extent they validly measure actual behaviours.
Twenty studies are discussed in which the relationship between self-reported and actual behaviour was considered inconsistent and problematic. Socially desirable responding has received the greatest attention, but individuals may consciously or unconsciously bias their responses by lying, imagining or omitting information. In addition, a driver’s ability to self-report accurately can be affected by psychological limitations such as memory.
However, one of the most serious issues is lack of due diligence by researchers in relation to the format and context of self-reporting questions, something that researchers themselves can easily attend to.
A researcher can improve the accuracy of self-reporting format and context by: providing appropriate time scales for responding; seeking objective sources of data where possible; carefully defining terms; assuring confidentiality of responses; identifying individuals who erroneously believe inappropriate driving behaviours such as speeding are really quite safe; considering the use of pre-determined response categories; and considering having a control group not exposed to a campaign or other intervention.