the laboratory's first survey to examine the environmental effects of road building was carried out at alton, hants in 1971 and 1972. alton is a town of about 10000 population situated on the a31 between farnham and winchester, to which a by-pass to the south of the town was opened in september 1971. the survey was in two parts: a 'before' carried out in july 1971 and an 'after' in july 1972. it consisted of noise measurements, traffic measurements and opinion questionnaires of residents, of shop and office workers and of pedestrians. the survey was based on the main road (a31) through alton with two control areas, one in alton away from the main road and the other at bentley, a village on part of the a31 which is not affected by the by-pass. a year after the by-pass had opened, in the centre of the town traffic had decreased by about 40 per cent (heavy goods vehicles by 60 percent) whereas the average noise level - 18 hour l10 - had decreased by less than 2db(a). nearer the edge of the town, traffic had decreased by about 55 percent and the average noise level - measured at house facade or no more than 10 metres from the near kerb - had fallen from 70 to 64db(a). opinion surveys showed that whilst people appreciated the improvements traffic was still a nuisance. for example, a year after the by-pass was opened 50 percent of the high street residents said it was less noisy but the proportion who were ever bothered by noise or vibration only decreased from 65 to 50 percent. (a).

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