Categories
air quality

Widen roads to reduce vehicle emissions? Really?

Sheffield City Council Business Case, 2018 [Link]
Sheffield City Council Funding Bid, 2017 [Link]

We often hear these claims, but very rarely are they backed up by evidence. Normally they’re just stated, like in the two examples above. I went looking for the evidence and this is what I found.

The basic premise is that vehicles speeding up and slowing down produces more emissions than vehicles travelling at a constant speed (smoother traffic flow), that it will take each vehicle longer to travel through an area, therefore increased emissions. This argument is used to argue against speed bumps, traffic lights, lower speed limits and 20mph zones, and is used in favour of schemes to reduce congestion.

However the counter argument is that decreasing congestion by increasing road and junction capacity (to reduce delay and queuing) will increase traffic levels through a process known as induced travel, or latent demand (the idea that people choose a different route, mode or time to make trips because of congestion).

So, there’s a trade off, it’s likely that early results will show an improvement in air quality, but changes in travel patterns over time will lead to an increase emissions in the medium term. For more information about induced traffic see WikipediaCampaign for Better TransportWired.

Bigazzi, Alexander York, "Trafc Congestion Mitigation as an Emissions Reduction Strategy" (2011). Dissertations and Teses. Paper 131. 10.15760/etd.131
Bigazzi, Alexander York, “Trafc Congestion Mitigation as an Emissions Reduction Strategy” (2011). Dissertations and Teses. Paper 131. 10.15760/etd.131

Studies that assume that the number of journeys are fixed, will not include the possibility that pollution will increase due to increased trips.

If you’re looking at a scheme where it’s claimed air quality will be improved, always check if the study assumed that the number of trips is fixed and won’t change.

I don’t know how common this claim is around the UK/World, but in Sheffield I’ve read it a number of times. For example, the 2017 A61 Inner Ring Road scheme will “reduce congestion which will improve air quality”.

There is academic research in this area, some of which involves micro-simulation of vehicle movements. There are 2 studies from 2003 and 2006 with the same author, the first looked at 2 merging roads and traffic signal synchronisation, and the second paper looked at a motorway merge.

In summary, the studies found 10 to 30% reduction in pollutants if traffic levels remained the same, but that pollution would be increased if traffic levels increased by 15 to 30% (depending on the scenario modelled).


The key research is:

R.B. Noland, M.A. Quddus / Transportation Research Part D 11 (2006) 1–14, “Flow improvements and vehicle emissions: Effects of trip generation and emission control technology” [Link]

Fotis Stathopoulos and Robert Noland, Issue. 1842, : Pages. 57-63
(Issue publication date: January 2003) /Transportation Research Record: Journal of the Transportation Research Board / “Induced Travel and Emissions from Traffic Flow Improvement Projects” [Link]

The research in this area was summarised in 2011 in a masters thesis and is well worth a read.

Bigazzi, Alexander York, “Traffic Congestion Mitigation as an Emissions Reduction Strategy” (2011). Dissertations and Theses. Paper 131. [Link]

Categories
20mph air quality council

Sheffield Public Health Report 2014 – Climate Change and Health

Climate Change and HealthThe annual Sheffield public health report has been published and this year the focus is on Climate Change. All of the topics in the report impact both public heath and climate change.

Climate change is the defining public health issue of this century.

I’m very happy that such an important issue is right at the top of the public health agenda in Sheffield.

There are however links between present public health problems and the kind of steps we have to take to tackle climate change. Many of the things we need to do to reduce greenhouse gas emissions will benefit our health in the short term, too. We describe some of those things.

This is quite a good video of Dr Jeremy Wight explaining his annual health report.

As we know all too well, many the things that will help with climate change will help with more short term public health problems and Jeremy Wight sums this up very succinctly.

Active travel (walking and cycling) and public transport increases physical activity and social connections, improves physical and mental health, helps people stick to a healthy weight, and reduces harmful air pollution and greenhouse gas emissions.

The recommendations focusing on active travel are right at the top of the list.

  1. The Council should develop and implement a programme of signposting walking routes with the time it takes to reach the destination.
  2. Sheffield people should consider traveling short distances on foot or by bicycle rather than by car, and sign up to ‘Move More’ at www.movemoresheffield.com.
  3. The Council should commit to increasing the number of 20 mph zones within the City as quickly as possible.

I don’t think that the reports recommendations for active travel will bring about a big enough shift on their own, there seems to be a focus on encouraging (signposing walking routes, people should consider travelling short distances on foot or by bicycle) rather than creating an environment where this is normal and designed in everywhere so that walking and cycling are real choices.

I wish that the recommendations in this report were more robust and pushed us to change the way we design our streets. We’ve seen examples in Sheffield recently where the walking and cycling environment has been eroded to increase capacity and reduce delay to motor traffic. Until we improve the environment, the encouragement will be wasted and we’ll only reach small numbers of people willing to cycling in today’s uninviting and hostile conditions, the low hanging fruit.

However, judging by the response I’ve heard Dr Jeremy Wight got at the council meeting where this was presented, he’s going to need all the support he can get!

His presentation drew an extraordinarily negative response from Labour and Lib Dem councillors, from which there is much to learn. [source]

The discussion also revealed that the chair of the Sheffield Council Cycle Forum, Peter Price, isn’t convinced about climate change being caused by carbon dioxide emissions!

One Labour councillor admitted to being a climate change sceptic (he believes CO2 emissions are due to global warming, not vice versa); [source]

We have the 20mph recommendation which should help to slow down traffic on our streets. Sheffield is very keen on 20mph areas and 11 more areas are planned for the coming year (10Mb pdf map). I’m still nervous that 20mph as we’re rolling it out will have as big an impact as we’re hoping, I think that it needs to be accompanied by a reduction in traffic volumes too, the benefits are amplified when the volume of traffic is reduced. There seems to be a slow realisation that there are problems with our main roads (which haven’t historically been included in 20mph areas) and we’re beginning to see ‘advisory part time 20mph limits’, a top for another post.

Whilst improved road safety alone justifies 20 mph limits, air pollution and traffic noise drop when speed is reduced and streets become more pleasant and attractive places. Increased use of shared public space contributes to an increase in social capital.

Link to the Sheffield Public Health Report 2014.

Edit 07/01/2015

The Star have reported today that Dr Jeremy Wight is resigning.

Edit 27/01/2015

The Shields Gazette has published an interview with Jeremy Wight discussing some of this. he says that “it’s absolutely not true that that [response to his report] has contributed to my decision to leave”.

Dr Wight recently presented his annual report to Sheffield councillors.

Some suggested he was given a bit of a rough ride for choosing to focus on climate change in his report. He said: “Last year, for 2014, I made the theme of my report climate change and health.

“I think that if you look at what the big health issues are going to be for the rest of this century, I think climate change is number one.

“If the predictions about climate change come true, it affects every aspect of our ability to lead healthy lives, including food production and water supply.

“People have made some very, very grim forecasts. The reason I chose to focus on it is because there are things that we can do now that will help to mitigate the impact of global warming.

“For example, fitting better insulation in your home. If people used more physically active transport, that is good for people’s health and reduces emissions.

The response to his report was not the reason he chose to leave.

He said: “I think the response was that there are a lot more pressing problems now like the impact of welfare reforms. But it’s absolutely not true that that has contributed to my decision to leave.

The Shields Gazette, 19th January

Categories
air quality

Sheffield City Council object to 60mph on M1 in opposition to official policy

Sheffield City Council’s response to the DfT consultation goes against officially stated council policy of supporting lower speed limits on the M1. Their opposition to lower speed limits cited concerns about the economic impact, public reaction, enforcement and investor perception of Sheffield.

M1MMWe have air quality problems in Sheffield. We have an air quality action plan that calls out the M1 double decker viaduct as a problem. The area around the M1 is called Tinsley and the air quality is notoriously bad and breaches EU limits for NO2 for most of the year.

The DfT decided that they’d like to add an extra lane to the motorway and a consultation was launched to find out if people think reducing the speed limit to 60mph is something we should do to offset the damage. Sheffield Council submitted a response that was summed up as.

Unitary, county and district authorities… responded with detailed comments on the proposal, but all except Nottinghamshire County Council were ultimately opposed to the proposal.

Jack Scott, cabinet member for the environment disagreed that this was the response, he said that SCC wanted lower speed limits, will continue to lobby DfT for lower speed limits and planned to write to the DfT because they had misrepresented SCCs response. These tweets have now been deleted from Jack Scott’s Twitter feed. I couldn’t agree more with his views and the council’s policy on this, they’ve got it right.

Jack ScottWrite to DfT

The Sheffield Star newspaper has covered reactions to the decision. Jack Scott is quoted as “We have been let down massively – lives are being put at risk” and Sheffield MP Clive Betts said “The Government is showing complete disregard for the health and welfare of my constituents in Tinsley.”

The Sheffield Air Quality Action Plan includes policy to support lower speed limits.

Sheffield Air Quality Action Plan on M1 Policy
Sheffield Air Quality Action Plan on M1 Policy – Available here

However Sheffield City Council’s consultation response objected to lowering speed limits.

I think it’s disgraceful that there are still people in Sheffield City Council who trade off the lives of people against the perception of Sheffield to investors.

The City Council is concerned about the economic impact on the Sheffield City Region of the reduced speed limit on the 32 mile stretch of the M1 for an indeterminable time period. The Highways Agency has not modelled or made clear what the full impact of the proposed speed limit on the [sic] will have on the surrounding road network, the local economy and the development aspirations of South Yorkshire and the Sheffield City Region.

Sheffield City Region, along with the South Yorkshire Passenger Transport Authority (who have responded separately to this Consultation) would therefore, like the Highways Agency to further clarify and provide appropriate evidence on the potential economic impact of the Smart Motorway proposal operating at a maximum 60mph speed limit.

It is unclear how the speed limit will be enforced (and how the public will react) to ensure the claimed effect of mitigating the impact, particularly on air quality.

There is also an unresolved issue of ‘perception’ which is likely to affect the attractiveness and competitiveness of the Sheffield City Region in our desire to seek much needed inward investment. Such investment may be deterred if it is perceived that the sub-region required such onerous measures to deal with existing or likely future problems whereas others do not (in part at least through previous investment in national infrastructure).

It’s very clear that there is strong support for lower speed limits from the top of Sheffield City Council, it’s supported by cabinet members and council policy, however we need to find out why the official council response opposed lower speed limits.

Sheffield City Council’s official response to this consultation can be found here.

The Sheffield City Council Air Quality Action Plan can be found here.