Abstract
In the SWOV-report 1971-2, the six questions related to data acquisition and reduction are formulated. In this memorandum an attempt is made to analyse these questions thereby developing a concept of homogeneity of a traffic flow on a stretch of roadway, comparing of speed measurements made by radar and time recorder apparatus, describing the possibilities of traffic flow investigations by aerial photogrammetry, and treating the probable influence of detector cables on traffic flow characteristics.