Context 144 - May 2015

C O N T E X T 1 4 4 : M A Y 2 0 1 6 23 MATTHEW CHAMPION The hidden impact of HGV vibrations Official advice and guidance relating to the impact of vibration from heavy goods vehicles (HGVs) on historic buildings is out of date and misleading. It’s time for a reassessment. In the late 1960s and early 1970s the general public and a number of heritage professionals began to express concern that the increasing levels of traffic on the nation’s roads were causing worrying levels of vibrations that, in turn, were leading to the damage of historic buildings, particularly those close to major roads. A number of studies undertaken (Crocket, 1966; Crocket, 1973; Civic Trust, 1970) which, combined with high levels of anecdotal evidence, suggested that traffic-induced vibrations were the cause of structural damage in historic properties.With traffic levels, and vehicle size, predicted to increase dramatically in the coming decades, it was anticipated that such structural damage from vehicle vibrations, in particular heavy goods vehicles (HGVs), would also increase. Faced with these concerns, theTransport and Roads Research Laboratory (TRRL) instigated a series of scientific experiments, based upon individual case studies of historic buildings, designed to investigate and evaluate the potential for structural damage caused by traffic-induced vibrations.These tests were undertaken in the mid-1980s, with the survey work undertaken by the civil engineering division of English Heritage. The results of the tests were published by theTRRL as TRRL Research Report 156 and TRRL Research Report 207 .These two reports were then supplemented with an updated report, combining the two earlier reports and including supplementary information,which was published in 1990 as TRRL Research Report 246 . These three reports form the basis of all subsequent design and planning advice in relation to the effect of ground-borne HGV vibrations on historic buildings. Current planning advice with regards to the possible effects of ground-borne vibrations on buildings is contained in the Design Manual for Roads and Bridges (revised 2011) and is also based solely on the conclusions of the TRRL reports. All three reports stated in their conclusions that there was no evidence that traffic- induced vibrations caused structural damage to historic buildings. However, re-examination of the original survey data on which the reports were based suggests that such conclusions do not fully reflect the findings of the actual surveyors undertaking the fieldwork. The original data on which the TRRL reports were based took the form of eight individual case studies of historic buildings that were subject to high levels of vibration caused by HGV traffic.The buildings studied varied a great deal in terms of construction type, location and state of preservation. Each was surveyed over a period of time in the late 1980s by qualified surveyors working for English Heritage. The sites included the church of St James in Louth, Lincolnshire, a cottage in