Letters, January 20, 2011, part three

No proof speed humps calm traffic

SIR – Mr Metcalf (Herts Advertiser, January 13) queries my assertion that traffic-calming measures cause extra vehicle emissions. He then seeks to use 30-year-old German research on emissions at different speed limits when there is no reference as to whether or not there was any traffic calming in any of the roads researched.

I prefer data that is more up to date, more specific and closer to home. The Transport Research Laboratory in the United Kingdom conducted emissions tests on roads with a 75-metre hump spacing and found CO emissions increased by 70-80 per cent, hydro-carbons by 70-100 per cent, and CO2 by 50-60 per cent.

In the draft Local Transport Plan the aim of “to reduce transport’s emissions of carbon dioxide and other greenhouse gases”, is given a greater priority than the aim of “to contribute to better safety security and health and longer life-expectancy by reducing the risk of death, injury or illness arising from transport”. It would seem to me that in view of this order of priority it is incumbent on the county council to reduce transport’s emissions by removing traffic calming measures that the TRL has proven cause extra emissions. If the county council does not do this then it will be failing both in its response to government requirements on it and in its duty of care to its residents.


Forge End, St Albans

SIR – John Metcalf claims that speed humps are good for the environment and for road safety. He is wrong on both counts.

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With regard to the environment, he assumes vehicles will maintain a constant speed over and between humps. That is pure wishful thinking. A few drivers may keep to a steady speed, but most will increase speed between the humps, and those changes of speed will increase emissions. He is also very selective in his choice of “evidence”, citing some “research” conducted in Germany in the 1980s!

I’m always suspicious when someone quotes from a very old study, especially from another country. Engines have changed dramatically over the last 25 years (fuel injection, catalytic converters, popularity of diesels, hybrids) and 1980s engines were not designed to meet strict emission and fuel consumption targets. Humps also create noise (which disturbs residents) and shock vibrations (which can damage buildings and underground pipes and sewers). They are bad for the environment in all respects.

But more dangerous than his environmental argument are Mr Metcalf’s views on safety. There is no evidence anywhere in the world that speed humps reduce collisions or casualties. There is, however, evidence of the damage caused to suspension, steering, tyres, etc..

A report by Warranty Direct a year ago estimated the average annual vehicle repair bill for damage from speed humps and potholes to be �240. It is inconceivable that this level of damage has not resulted in crashes caused by latent failures, invariably miles away from the humps and possibly at speed on a motorway. I have also seen estimates of deaths resulting from ambulances taking longer to get to hospitals where the route involves humps.

Herts County Council’s own guidance acknowledges that humps generate noise and can be uncomfortable for drivers and cyclists. They ignore their other unwanted side effects described above.

There is no case for speed humps and they need to be removed from our roads.

A final thought – how much “road rage” has been fuelled by “traffic calming”?


Evans Grove, St Albans

SIR – It would be better if speed humps were properly maintained. The hump in Belmont Hill at the Holywell Hill end is way out of specification at the southern end, as shown by the number of gouges taken out of it. I have reported it three times over the years and nothing is done.

I have made other reports about defects, and it seems that the method is to leave them for six months and then mark them as completed. This no doubt looks good on the statistics, but does not help improve the environment.

The overgrowing hedges by the nearby pelican crossing on Holywell Hill and another on the river Ver bridge have both been reported and are markled as comleted when they are not. The blocked gulley on Holywell Hill by Dean More Close is still untouched.

Perhaps if jobs were only marked as completed when they really were, a truer picture of the state of the roads would be apparent. Those are just my reports, but I suspect that it will be the same for others too.


Holywell Hill, St Albans