Road Safety News

20mph limits and re-designing speed bumps key to reducing transport pollution: NICE

Thursday 1st December 2016

Health experts are calling on local authorities to introduce more 20mph speed limits in congested residential areas in an attempt to reduce air pollution.

Published today (1 Dec), new draft guidance from the National Institute for Health and Care Excellence (NICE) also calls for speed bumps to be redesigned, to stop cars speeding up and then slowing down between them.

The RAC has welcomed the guidelines, saying there is plenty in the draft that is worthy of ‘serious consideration’.

NICE says that being exposed to short-term and long-term air pollution caused by human activities can have a significant health impact, with harmful emissions and the environmental risks associated with pollution linked to around 25,000 deaths a year in England. It also says that air pollution and its health impact costs the UK up to £18.6bn annually.

NICE estimates that road traffic causes more than 64% of air pollution in urban areas, and as a result it is urging local authorities to do more to tackle the problem.

Other recommendations laid out by NICE include:

  • Restrictions on engine idling during short stops such as outside schools and hospitals
  • More charging points for electric cars in residential areas
  • Placing the most commonly-used rooms in new houses away from polluting roads

NICE is also calling on businesses and transport services to educate their transport staff in more efficient ‘smooth’ driving skills, such as avoiding hard accelerations or decelerations and turning off the engine when at a standstill.

Professor Paul Lincoln, chief executive of UK health forum and NICE guideline committee chair, said: “Traffic-related air pollution is a major risk to public health and contributes to health inequalities.

“The NICE guidance sets out a strategic range of evidence-based practical measures to encourage low or zero emissions transport. This is very timely given the imperative to meet EU and national air quality standards.”

Nick Lyes, RAC roads policy spokesman, said: “While only in draft form at this stage, there is a lot in NICE’s guidelines that is worthy of serious consideration when it comes to tackling air quality.

“No idling zones, and the suggestion that local authorities should think again about speed humps which cause motorists to brake and then accelerate again, are eminently sensible suggestions and both have the potential to improve the quality of air locally.”

NICE’s draft recommendations on tackling air pollution are out for public consultation until 25 January 2017. 

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So the problem then is not actually road humps at all, but diesel vehicles (you make them sound almost undriveable in the towns Bob!) and drivers of petrol vehicles who require some education on driving smoothly which is one of the things NICE are recommending anyway. There's a virtue in smooth driving at steady speeds with minimum acceleration and decceleration. (Might also prevent a lot of collisions into the bargain.)
Hugh Jones, Cheshire

Agree (3) | Disagree (2)

I think (editor) that your headline overstates the point about 20MPH limits. The NICE draft guideline says only: "Consider 20-mph zones in residential areas characterised by stop–go traffic where this will reduce accelerations and decelerations."
David Davies, London

Agree (3) | Disagree (0)

The average car ? does 90 mpg at 20 mph. Yes engine only on a test bed with a constant rev. No ups or downs or corners or bends or stops or starts. No vehicle made will do 90 mpg around any track or on any road at a steady 20 mph. Its not mechanically possible. VW proved that. All its fuel economy and emissions were based on a they have for every car manufacturer since time immemorial.

As for diesel vehicles they are not designed to potter round town at 20 mph, if they do they will actually break down within 18 months and then need basically a new engine. The gasses they give off clogs up the engine through its air intake and gives up. Without high mileage and at speed the diesel engine will fail. Diesel engined busses as one example are stripped down annually and cleaned out of particulates clogging up the air intake. Ever been behind a diesel when it accelerates fast it blows out black particulates that are clogging up its hot air intake return valve.
Bob Craven Lancs

Agree (8) | Disagree (2)

The average car does 90+mpg at a steady 20mph. Its the constant acceleration that pumps up exhaust emissions and deceleration that pumps up brake and tyre emissions.

If you want to drive at a steady speed over speed bumps its easy. Just slow down to a constant 20mph or less (whatever is comfortable) and get 90mpg.

Compliance is pretty bad on all signed only limits. For those complaining then its an engagement and enforcement issue. If they were to put as much effort into that as they do to moaning about compliance then they wouldn't have to moan.

DfT findings show that on free flowing 30mph roads 52% of cars are below 30mph whilst on free flowing 20mph 53% are below 25mph. Average speeds are 6mph lower as well.

Imperial College found an 8% reduction in NOx and PM10 in diesel vehicles for 20mph limits as opposed to 30mph.

Lower speeds are also key to making places better for healthier walking and cycling.

So yes, communication by speed bumps is very much by "buttocks and spines", the far better way is "hearts and minds".
Rod King, Cheshire, 20's Plenty for Us

Agree (5) | Disagree (8)

Unless Derek, they're just calling at the retail park's/supermarket for cheaper fuel of course, in which case nothing to carry. Presumably you wouldn't want the reputed damage causing, pollution causing humps to be removed from these 'dangerous places for pedestrians'? Does Stats 19 confirm that by the way? I would have thought conventional roads with generally faster moving traffic, myself.
Hugh Jones, Cheshire

Agree (0) | Disagree (4)

To Bob Craven; the B4373, Avenue Road and Ironbridge Road, Broseley, Salop. Installed, moved, then removed completely.
Derek Reynolds, Salop.

Agree (3) | Disagree (0)

A speed hump cosmetic? As in improving the looks of a road? Unbelievable.

Hugh, supermarket car parks are amongst the most dangerous places for pedestrians. But it is where the consumer needs to park in order to load their vehicle with a trolley full of groceries that cannot be carried in two hands.
Derek Reynolds, Salop.

Agree (4) | Disagree (0)

My car comsumes 5-6mpg more at 20mph than at 30mph.
David Weston, Corby

Agree (6) | Disagree (2)

I wonder what the effects of pollution levels are like in retail parks and large supermarket car parks where there is a high density of slow-moving vehicular traffic mingling with pedestrians and typically, unregulated speed humps far more severe than you would find on the highway.

I suppose conveneience and the thought of a bargain must temporarily overide people's concerns over health and their vehicles. I think the public are prone to what one might call transient and selective concerns.
Hugh Jones,Cheshire

Agree (3) | Disagree (4)

A good way to reduce pollution would be to reduce commuting, both cars and trains pollute the atmosphere. Stop London building any more workplaces in the centre. Ban people from working more than ten miles from home (some hope!)
Robert Bolt Saint Albans

Agree (3) | Disagree (2)

I doubt very much that speed bumps and or cushions are ever installed for purely cosmetic reasons.

When it come to a question as to whether speed humps should be employed as a deterrent where the speed limit has say been reduced to 20 mph there is already an existing formula and guidelines applied and it therefore becomes a norm under some circumstances to automatically require such humps to be laid. This negates any consultations made before or indeed after the event. So there would be no requirement for further or subsequent consultations that would result in such humps being removed. As said there would be an additional cost to that together with a possible admission that they were a mistake and not required. As a result their removal will not take place. I know of no areas where humps have been employed and later removed. Has anyone else have such knowledge? Perhaps they could share that info with us?
Bob Craven Lancs

Agree (2) | Disagree (0)

If speed humps have been installed for purely cosmetic reasons, this will be simple advice to follow.

But, speed humps, like all traffic calming measures, have been installed for a reason or a number of reasons - whether it is to ensure a 20mph limit is adhered to or to reduce speed of traffic due to a record of collisions or in response to local requests and campaigning or outside a school. There will need to be a review of each one to consider whether they are effective in achieving their original aims, whether they are still needed and the relative cost: benefit of removal. E.g. if the air pollution issue is low but the potential casualty risk is high, the decision may be different to somewhere where the opposite applies.

Whatever the outcome, these studies will require engineers and others to undertake them, which costs money. Without funding to pay for this additional work it will be very slow progress other than in Air Quality Management Areas.
Honor Byford, North Yorkshire

Agree (3) | Disagree (2)

". . calls for speed bumps to be redesigned, to stop cars speeding up and then slowing down between them."

Then remove them. That's the simple answer.

Brosely, Salop. had a series of speed humps installed along one through road along with a pavement build out stopping traffic in one direction and forcing it onto the 'wrong' side of the road. The humps lasted less than one year before being removed though the build out remains and has been driven into several times. After the humps were removed traffic once again drove smoothly with less discomfort, damage and pollution. Remove them.
Derek Reynolds, Salop.

Agree (6) | Disagree (2)

Don't forget noise pollution Pat. The quiet rural areas of North Wales which I used to cover and which were on routes popular with bikers, regularly suffered from and complained about noise pollution from motorcyclists accelerating unnecessarily excessively and seemingly not deterred by animal droppings on the c/way. You're no doubt a sensible, respectful biker, but many aren't. It's not the same pollution as NICE are concerned about perhaps, but still stressful enough to affect people's health.
I think a certain degree of pollution of one form or another from modern traffic is unavoidable, but I'm sure it doesn't have to be as bad as it is.
Hugh Jones, Cheshire

Agree (4) | Disagree (3)

Is this a city-centric policy for a city-centric problem? In many parts of the English and Welsh rural communities we don't have much problem in the way of air pollution from vehicles. As a biker, I am much more concerned about the emissions from horses and cows on the highway than vehicle exhausts. Can we have some 'rural-proofing' of NICE policies please?
Pat, Wales

Agree (8) | Disagree (6)

or...maintain the same speed over the bumps and in between - which I think is probably the idea anyway. Who'd be bothered to repeatedly speed up and slow down again?
Hugh Jones, Cheshire

Agree (8) | Disagree (7)

As we already have high levels of non-compliance in many areas with 20mph speed limits, all we will do with more of them is increase the levels of non-compliance. If you want more 20s please address the elephant in the room (non-compliance) first.
Pat, Wales

Agree (9) | Disagree (3)

How about removing all unnecessary speed humps and then traffic can travel at a constant without the need to constantly accelerate and then brake or slow and that would be a solution to improving exhaust pollution at little cost. Or would that be considered too much of a new way of thinking?
Bob Craven Lancs

Agree (15) | Disagree (8)