Community response to railway-induced building vibration
This study is an investigation of the subjective response to railway-induced building vibration. No previous study has obtained both subjective and objective measures from so many lineside residents: several hundred were interviewed and over fifty of the dwellings provided a site for a continuous 24 hour recording of building vibration. Annoyance caused by railway-induced building vibration, and the factors affecting annoyance, were investigated in a social survey. Of a sample of 720 adults living within 100 metres of railway lines in Scotland, 459 were interviewed; 160 of these noticed railway-induced building vibration. It is estimated that 1.4% of adults in Scotland notice railway-induced building vibration. Vibration was found to be amongst the least annoying aspects of a railway's presence in a neighbourhood. Vibration was recorded in 52 dwellings for 24 hours continuously in three axes. A method of isolating the portions of the 24 hour acceleration time-histories which represented perceptible railway-induced building vibration was developed. The severities of the isolated periods of the acceleration time-histories were assessed by 90 alternative measures chosen using the results of laboratory experiments. These had suggested that a vibration dose value (incorporating a fourth power relationship) was the most appropriate measure. The 90 measures were formed from combinations of different frequency weightings, time dependencies, averaging procedures and summing methods. Within-building differences in frequency and severity of vibration were found and differences occurred between similar, neighbouring, buildings. Frequency of vibration was influenced primarily by the characteristics of the building or the ground, rather than those of the passing trains. Horizontal vibration was generally below perception thresholds. The effect of different integration times used in root mean square averaging was demonstrated. No clear relationship was found between distance from the railway and severity of building vibration. Subjective response was found to be influenced primarily by the number of trains passing in 24 hours but not significantly affected by any of the characteristics of the vibration. It is concluded that this arose because railway-induced building vibration did not cause significant annoyance within the sample population. This conclusion does not deny the existence of individuals who were annoyed, or of individuals whose annoyance was influenced by the characteristics of the vibration. The conclusion that railway-induced building vibration did not cause significant annoyance within the sample population could not have been obtained from the questionnaire data alone. This demonstrates the importance of obtaining both objective and subjective measures when investigating subjective response to phenomena such as building vibration.