Among the different sources of environmental noise, Road Traffic Noise (RTN) has become the main acoustic pollutant in urban and suburban areas in recent years negatively affecting the quality of life of their citizens. In order to address this problem, the European authorities require their member states to fulfil the European Environmental Noise Directive 2002/49/EC by tailoring noise maps and develop the corresponding action plans for major agglomerations and key infrastructures every five years. In recent years, different technological advances have allowed the development of the so-called Wireless Acoustic Sensor Networks (WASNs) as an alternative to the costly expert-based generation of noise maps. Among the different WASN-based attempts focused on the ubiquitous monitoring of environmental noise, the LIFE DYNAMAP project has developed a WASN- based dynamic noise mapping system for the monitoring of RTN through dynamic noise maps in Italy. After deploying two WASNs, more than 310h of acoustic data have been collected from the 24-nodes installed across the District 9 of Milan (urban area) and the 19-nodes placed along the A90 highway surrounding Rome (suburban area). The study focuses on the analysis of those acoustic events unrelated to regular RTN −denoted as Anomalous Noise Events (ANEs)−, as they may bias the generation of the RTN noise maps critically. To that effect, the individual and aggregated impact of ANEs on the A-weighted equivalent RTN levels is evaluated considering a 5-min integration time according to the project specifications and three impact levels (low, medium and high). The results show that both individual high-impact ANEs (e.g., sirens, horns, etc.) and aggregate low and medium-impact can bias the computation of RTN noise levels critically, thus, making the automatic removal of ANEs a key process in the generation of reliable dynamic RTN noise maps.