Experimental investigation of the effect of roundabouts on noise emission level from motor vehicles

Roundabouts can provide benefits in many ways. They are safer, more efficient, less costly and more aesthetically appealing than standard at-grade intersections (controlled and signalized). The administrations have often identified roundabouts as a proven safety countermeasure for the following reasons: a) reduce overall conflict points and remove left-turn conflicts; b) reduce the vehicle speeds; and c) reduce accident severity for all users, allow safer merges into circulating traffic, and provide more time for all users to detect and correct their mistakes or the mistakes of others due to lower vehicle speeds. Also, from an operational point of view, roundabouts offer the following significant advantages: a) may reduce delays and queues than other forms of controlled intersections; b) can reduce lane requirements between intersections, including bridges between interchange ramp terminals; and c) create possibility for adjacent signals to operate with more efficient cycle lengths where the roundabout replaces a signal that is setting the controlling cycle length. Furthermore, roundabouts can provide important environmental benefits reducing delays and the number and duration of stops. Even in heavy traffic, vehicles keep moving in the queue rather than coming to a complete stop. This may reduce significantly noise and air quality impact as well as fuel consumption by reducing the number of acceleration/deceleration cycles and the time spent idling. In this article, the environmental aspects associated with roundabouts are treated with reference to issues related to noise production. The experimental investigation will refer to a heterogeneous succession of intersections (standard intersections, two-way stop-controlled and roundabouts) characterized by homogeneous traffic flows. The results of the research are interesting and contribute to consolidate the awareness, already highlighted by other international studies, of the role of roundabouts as effective measures to mitigate traffic noise. (C) 2019 Institute of Noise Control Engineering.