One of the most important problem in the analysis of city logistics systems is data collection. The solution, which could support this process is utilization of independent, easy to use devices. The paper is focused on the example of utilization the portable road traffic detectors. These devices are easy to use tools, which can help to collect traffic data including the vehicles classification. The Authors will introduce an example of practical utilization of this kind of device, Sierzega SR4, as well as the advantages related to that.