In built-up areas, an increasing number of persons are affected by road traffic noise while performing mental work. This experimental study focused on annoyance and mental strain due to various noise scenarios. A total of 102 healthy, young persons (51 women, 51 men, aged 18-31 years) were randomly assigned to one of five experimental conditions determined by traffic flow (even, lumped) and traffic composition (20%, 40% heavy vehicles). While exposed to noise they performed a grammatical reasoning and a mathematical processing task. Performance and mental strain were not affected by any of the five noisy conditions. Individuals with high noise sensitivity were partially more annoyed and performed less than persons with low sensitivity. STATEMENT OF RELEVANCE: The present study provides information about mental strain due to tasks with different cognitive demands and the role of noise sensitivity in various traffic noise conditions. The results show that measures aiming at the reduction of the proportion of heavy vehicles should additionally consider particular traffic flow.