Effects of urban morphology on traffic noise: A parameter study including indirect noise exposure and estimated health impact

Noise exposure has been calculated and analysed for 31 different urban morphologies in an urban setting. For five of the urban morphologies also vegetation surfaces on facades and roofs were studied. Facade exposures were analysed for both smaller (single-sided) flats and larger (floor-through) flats, considering the direct exposure from the roads as well as the indirect exposure at noise-shielded positions like inner yards. Also, grid map area exposures at ground level were calculated and analysed for both sidewalk and yard areas. The facade exposure levels, using indicators Lden and Lnight, were used to estimate annoyance and sleep disturbance as well as disease burden in terms of DALY (Disability-Adjusted Life Years) per person. In all urban morphology cases, single-sided flats showed overall better performance (i.e. lower DALY) than larger, floor-through flats; however, the inclusion of a bonus for additional facade elements having a lower noise exposure gave the large flats a similar or better predicted overall performance compared with the small flats. Among the building types studied, for small flats and constant building density, the use of perimeter blocks with closed inner yards, slightly open yards and U-shaped buildings showed results of relatively better overall performance compared with I-shaped, L-shaped and point buildings. When the yards grow in size, the performance of closed inner yards dropped. As general trends, perimeter blocks were shown to perform better than morphologies with less enclosed yards and densification with constant traffic flow was shown to result in improved performance. However, building types with slightly open yards may provide an attractive compromise solution due to its relatively good noise shielding at the same time as enabling solutions to air pollution and corner-flat layouts. In addition, complementing the perimeter blocks with towers was shown to enable improvement. Furthermore, traffic concentration by locating all local traffic to a single road was shown to be beneficial, increasingly so by widening the road. Predicted effects of vegetation surfaces on facades and roofs showed significant overall improvement, where closed inner yards benefit from vegetated roofs. The area exposure results showed that when the building blocks are successively less enclosed the levels are reduced on the sidewalks and increased in the yards. Also, the benefit of facade vegetation is shown for the area exposures.