In order to develop an operational traffic conflict technique for local road safety assessments, reliability and validity should be tested. At ICTCT2011 and 2012 workshops, recent activities in the Czech Republic have been presented, aimed at developing a unified traffic conflict technique (TCT) applicable in Czech conditions. The two key properties of every safety indicator are reliability and validity. Therefore various practical ways to assess them in the Czech environment have been sought. Reliability may be tested as an internal consistency of observers (inter-reliability) or external consistency (intra-reliability). Validity may be evaluated as process or product validity. However, accident frequency, which has been traditionally used as a validity criterion, has been known to suffer from a number of biases; therefore alternative validity criteria are discussed, such as the probability of encounter or frequency of critical events in simulation studies. Preliminary experience is summarized and practical conclusions related to observers reliability and results validity are drawn. This publication may be accessed by Internet users at: http://www.ictct.org/workshop.php?workshop_nr=35
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