This purpose of this paper is to both demonstrate the importance of qualitative methods in travel behaviour research and explore the challenges researchers face in employing them. Qualitative methods offer a powerful tool for helping us understand the complexities of travel behavior. Methods such as focus groups, interviews, and participant-observer techniques can be used in conjunction with quantitative approaches or on their own to fill the gaps left by quantitative techniques.

Source:

http://www.des.ucdavis.edu/faculty/handy/Qualitative_paper.pdf