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When the hybrid buses on a line in Gothenburg were replaced with fully electric ones, the health of those who lived along the line improved, those are the conclusions of a study by the University of Gothenburg.
The line in question is somewhat hilly in places, which means the noise levels have been high when the hybrid buses have throttled up to climb slopes. The low-frequency noise that the buses generatemainly affects human health.
When electric ones replaced the buses, the low-frequency noise decreased dramatically. The proportion of the nearby residents disturbed by noise to a very high degree was reduced from 26 to 5 percent. The proportion who felt tired once or twice a week fell from 49 to 39 percent and the proportion who felt depressed went from 22 to 17 percent.
"It was an improvement, people felt significantly better. Although we can not say with certainty that the changes cover the entire population or persist over time, we believe that the results can be generalizable in residential environments where bus traffic constitutes a large part of the exposure. Given that other traffic in the urban environment will also be quieter, this can affect public health", says Kerstin Persson Waye, professor at the University of Gothenburg and one of the researchers behind the study, in a press release.
In the study, the researchers interviewed residents along the bus line and residents in other places, who acted as a reference group. In total, over a thousand people were included in the study. In addition, the researchers performed sound measurements in a number of homes, including indoors.
The reported health before and after the swich to electric buses was clear and statistically significant. This applied to both actual noise levels and what the residents themselves noted.
The low-frequency noise must be reduced.
"We can be disturbed by different sounds, but the concern with low-frequency noise is that it is attenuated to a lesser extent than high frequencies and therefore penetrates more easily into homes; even small level increases are perceived as very noticeable", says Kerstin Persson Waye.