This work studies the impact of the substitution of a traffic light for a modern roundabout on carbon monoxide concentration. The estimate of CO concentration is made by means of the CAL3QHC dispersion model, considering only passenger vehicles as emitting sources. Local traffic and meteorological parameters had been adopted and the emission factors had been estimated using CMEM emission model. The maximum observed values in eight different wind directions had been compared, considering both moving and queued vehicles. The adopted model showed that the maximum concentrations of CO in the roundabout scenario were about 50% of the obtained values with the use of the signalised intersection. Concentration maps analysis demonstrated that not only the maximum values are higher in the case of the traffic light, but the area of the concentration curves is larger. These analyses are important for proper environmental management and contribute to traffic engineers seeking environmentally sustainable solutions.
Keywords: environmental pollution, atmospheric diffusion, pollution dispersion, signalised intersection, roundabout, vehicular emissions