Portsmouth City Council is proposing a mini-Clean Air Zone class B which just covers the city centre. According to their computer models, this will be sufficient to get the city with legal pollution limits by 2022, which is assumed to be “as soon as possible” to comply with the law.

Area of the proposed mini-CAZ

The council are relying on predictions by computer models to determine what course of action to take. However, the quality of the predictions depend on the validity of their assumptions. There is a well known saying that if you put “garbage in” to a model, you will get “garbage out“. PCC has made many predictions over the years that have turned out to be false. For example, in the 2010 plan, PCC states they will reach legal levels by 2012-2016. In 2015, it was supposed to be below the legal limit by 2020. In 2017, it was expected by 2021. Their predictions have repeatedly failed. Now we are expected to believe their latest estimate that they will be legally compliant by 2022, but it does not seem that lessons have been learned from past failures. Policy making is suppose to take it to optimism bias but that apparently has not been used in air quality planning. The most likely sources of error are traffic growth estimates (driven by new developments), and the predicted shift to more efficient vehicles, but regardless of the specific cause, it is clear that something is very wrong.

Apart from the repeated failure of modelling, the case study data of similar class B clean air zones have shown only a slight improvement after their introduction. This does not meet the challenge that Portsmouth faces which requires around a 10-15% cut in NO2 pollution.

The computer models are not solely produced by PCC, but are done under a DEFRA (Department of the Environment, Fisheries and Rural Affairs) mandated methodology by an outside consultant. PCC has described some of the instructions by DEFRA as “deeply unhelpful“. It could be that DEFRA is using faulty models that are optimistic and will avoid central government having to tackle the problem, which saves them money. It is also likely that air quality consultants that involved model analysis are selected based on their willingness to tell the government what they want to hear. I have had private discussions with well placed people in which they have expressed concern over the validity of the modelling. Looking back that a recent debate, even Gerald Vernon-Jackson, the head of the council, said the scheme was being done “even though we know it will be ineffective“. Did Gerald just let the cat out of the bag? This contrasts with PCC’s public pronouncements that they have a workable plan. PCC is actually in a difficult position because they don’t seem to have the resources to tackle the air pollution problem independently and DEFRA will only fund the minimum scheme needed to reach legal pollution levels. If they go along with the mini-CAZ class B, which is the minimum based on DEFRA specified modelling, they are likely to fail in achieving legal pollution levels any time soon. If they object to DEFRA’s methodology, they fear they may get no funding at all. It’s either crumbs or nothing for poor Portsmouth!

The council has not done themselves any favours by repeatedly failing to explain the need of a CAZ and the benefits. In fact Gerald Vernon-Jackson was very clear that the CAZ scheme is not done by choice but rather that “this is a government imposed scheme“. This is going to leave people feeling more victimize rather than helped. A CAZ is primarily being introduced to improve public health after all! However, I must take issue over the claim it is being imposed. Strictly speaking, Portsmouth has a choice of implementing a CAZ or other measures that are at least as effective. The council, under various administrations, has had many years to tackle the problem had made no progress in reducing pollution levels. It is only due to their repeated failure that considering a CAZ has now been mandated. However, central government has also caused problems by dragging their feet on encouraging compliance and defusing to produce funding for schemes that would make a positive difference.

PCC are regarded by DEFRA to be a good example of how to plan to reduce air quality. Given the questionable effectiveness of PCC’s plan, it throws DEFRA’s judgement into doubt. This is further compounded by DEFRA trying to do a very targetting scheme back in 2018, again lead by dodgy modelling, which did not appreciate the city wide problem we face. Thankfully, due to PCC persuasion, we are looking at the city wide implications now.

The council has been busy for the last year on producing a new air quality plan that will be submitted to central government at the end of October 2019. In it they have modelled various types of clean air zones, such as a class C including light goods vehicles, and a class B excluding light goods vehicles. They make the claim that:

Class B CAZ is combined with a number of non-charging measures to ensure that compliance is achieved within the shortest possible time i.e by 2022. The alternative to this is to go to the Benchmark option of implementing a Class C CAZ which it is anticipated will achieve compliance in all locations by 2022, however it is anticipated that this will have a greater negative impact on Portsmouth’s residents and the local economy.

It seems absurd to suggest that the stricter class C will be no more effective than a class B CAZ. They get around this by rounding to the nearest year, so a false equivalence can be made. This is another trick by PCC to get out of achieving compliance “as soon as possible”, as required by law. It is also not clear why a class D, which covers private car usage, was not modelled. Common sense would seem to indicate that this would be even more effect and therefore be legally required. PCC better have good justification for this…

An additional annoyance caused by PCC is their self-congratulatory attitude given the air quality crisis and the climate emergency. When campaigners like myself point out the scope of what needs to be done, some councillors fall back on the tactic of listing their achievements. In some ways this is understandable because they have a very hard job and any progress seems to them like an epic win. In one case, a councillor was keen to point out how many solar panels have been installed and how we are one of the best in the county. Listening to their rhetoric, one might even thing they had the situation under control. However, progress so far has been just a drop in the bucket compared to what needs to be done. When considered in context, their attitude seems very complacent.

A concern with the restricted area of the proposed CAZ is it is less effective when compared to a city wide scheme. It also risks having traffic switch to routes outside the CAZ, making their pollution worse. I’d expect a significant increase in traffic down Copnor Road, the Eastern Road and possibly Albert Road as people avoid the charging area. Some of these roads are already over the legal limit or barely compliant, including Velder Avenue, Milton Market, Fratton Bridge, etc. PCC seems to be trying to redistribute pollution so the total remains the same but it is evenly distributed around the city!

As if we need further evidence of the harm cause by air pollution, additional studies have found a strong link between air pollution and heart attacks, strokes and acute asthma. It’s time to take the problem seriously!

The air quality plan is due to be submitted by PCC at the end of October. However, it is unclear when it will be available to the public. This needs to be circulated as soon as possible, because the measures will have a significant impact on the residents and businesses in the city. People need time to plan and adapt.

UPDATE: A version of this story was published in the Star and Crescent.