For information on survey materials visit:
Instruction Guide: http://www.bts.gov/publications/commodity_flow_survey/survey_materials/pdf/instruction_guide.pdf
Questionnaire used for quarters 1, 2 and 3: http://www.bts.gov/publications/commodity_flow_survey/survey_materials/pdf/questionnaire_q123.pdf
Questionnaire used for quarter 4: http://www.bts.gov/publications/commodity_flow_survey/survey_materials/pdf/questionnaire_q123.pdf
Commodity Code: http://www.bts.gov/publications/commodity_flow_survey/survey_materials/pdf/sctg_booklet.pdf