Speed Humps, Vibration and Noise by Jeremy Clyne (Article published in the BBRAG Newsletter in October 2004)
I am one of thousands of Londoners who have the misfortune to live next to a road hump (my home is in Streatham, near the picture above of the hump). As I said in written evidence to last year’s Greater London Assembly (GLA) inquiry into road humps, I have been driven to the extreme of hiring monitoring equipment which has recorded vibration four times above the level of acceptability. This shaking is usually accompanied by a loud intrusive crash.
GLA Report Missed the Point
My findings were recorded in the inquiry report “London’s got the hump” but the report’s authors completely missed the point I was making and referred to my submission in a section about “possible damage” to buildings caused by vibration, whereas I was complaining chiefly about the nuisance caused by vibration. Noise from humps was mentioned in the report but there was no reference to vibration nuisance, and so the issue continues to be ignored by traffic planners and engineers.
Vibration from traffic has long been known, at least since 1990, to cause “serious environmental disturbance” but the authorities choose to disregard these effects from road humps. For the past seven years I and other occupants of the building where I live have been subjected to regular intermittent disturbance from the vibration and noise caused in particular by heavy goods vehicles as they bounce off an unusually long (100ft) speed table. My inquiries and limited research lead me to believe that traffic engineers have disregarded the obvious effects on residents and that guidance being given to councils by the Department for Transport is grossly misleading when it comes to the nuisance that these traffic calming devices cause.
Vibration Exceeds Acceptable Limits
The results from my initial testing are startling, with vibration events regularly breaching the 1millimetre per second level of peak particle velocity at which complaint can be anticipated. I have even recorded events up to 4mm per second, four times above what is termed the “level of acceptability”.
The Transport Research Laboratory stated in its 1990 report Traffic Induced Vibrations In Buildings: “it appears that vibrations due to ground-borne traffic vibration may become unacceptable above a level of 1mm/s”. A later paper by Greg Watts, the TRL’s expert on the subject, “Vehicle generated ground-borne vibration alongside speed control cushions and road humps” (Control dynamics and man-made processes, 1998) reaffirms this, referring to “the guide PPV threshold values of 0.3mm, 1, 3 and 19mm/s for perception, complaint, fatigue damage and damage defined in BS 7385 respectively.”
Vibration a Common Source of Nuisance
The 1990 TRL report, which predates the widespread use of road humps, did not deal with the effects of humps but with traffic vibration generally, in particular from uneven road surfaces. Nevertheless it was stated clearly that “traffic induced vibration is a common source of nuisance affecting residents…………traffic vibration represents a serious environmental disturbance affecting large numbers of people” . The report also states that “ground-borne vibration is potentially a more severe problem (than airborne vibration) under the worst combination of conditions. This is because ground-borne vibration has been found to produce the greatest motion in floors and walls and to affect the whole building.”
Later it is stated “a ground-borne vibration problem is most acute when the building is within a few metres of a significant road surface irregularity such as a poorly backfilled trench or sunken cover”. The effects of traffic passing over a rough surface would, or should, have been apparent to any traffic engineer. Introducing road humps and speed tables with their much greater variation in surface height would have the obvious effect of creating much more significant vibration disturbance to adjacent properties. It has clearly been thought that these considerations were of little import compared with the perceived benefits of reducing speed.
Research Has Been Ignored
The lessons to be drawn from this research, namely that constructing road humps close to dwellings would cause unacceptable disturbance, have been ignored and road humps have been built everywhere rather than other forms of traffic calming being employed. Later research specifically on vibration from road humps details the “minimum distances between road humps and dwellings to avoid vibration exposure”. Minor damage, it is stated, would only occur if the road hump were nearer than a metre. Separately detailed are the distances recommended to avoid “perception” and “complaint”.
It is stated that on London clay a flat top hump (i.e. speed table) should not cause complaint (i.e. vibration above 1mm/s) to residents at a distance above 5 metres. And yet my home is suffering vibration four times above the level of acceptability, as can be seen in the evidence below, and is 6.5 metres away from just such a flat top hump.
From my experience and investigations it seems clear that the advice on recommended distances between road humps and residential buildings needs to be reassessed, as it appears that the guidance seriously understates the likelihood of vibration nuisance.
Vibration exposure from road humps is the subject of continued inquiry and research, probably because guidance given by official bodies bears little relevance to the reality experienced by those having to live with the problem. The issue is regularly the subject of academic papers. With regard to damage, TRL’s position is that only minor damage can result, and even that under fairly extreme circumstances. It is stated however in their 1990 report:
“a small additional stress imposed by traffic vibration might possibly add to a much greater static stress resulting in damage. Such a ‘trigger’ mechanism could perhaps cause premature failure in a building component already weakened by other causes. A more widespread concern is the possibility of fatigue damage occurring as a result of long periods of exposure to low levels of vibration. Buildings close to heavily trafficked roads may be exposed to many thousands of stress cycles each day so that the vibration dose over many years could be considerable.”
Cracks Appearing in Home
Cracks have appeared in my home but the difficulty is proving they are the result of vibration from the adjacent road hump, particularly when faced with the blanket denials from TRL of such effects. The fact that the property is shaken by heavy traffic can be shown and cannot be denied. And if TRL has got it so badly wrong in assessing vibration nuisance from road humps this puts a big question mark over its assertions about damage from road humps.
With regard to the particular problems I have experienced these have of course been reported on numerous occasions to my local authority, but to no avail.