So after more than a year’s wait, we have the Portsmouth air quality plan (technically called the outline business case or OBC). There are several associated reports along with this document. Portsmouth City Council are now waiting for approval from DEFRA before going to public consultation. Here are my first impressions:

The UK Plan states that local plans should seek to target measures so as to minimise their impact on local residents and businesses. […] Proposals that request government funding support demonstrate value for money; […] All short-listed and the preferred option must pass a Critical Success Factor test on whether the option proposed would deliver compliance in the shortest possible time. Additional factors, such as cost, can only be considered when options are equally effective at achieving compliance in the shortest possible time.

Mixed messages from the council but the last sentence reflects the actual legal situation, based on High Court rulings.

For most vehicle types (except LGVs), the Portsmouth fleet is older than the national average (see Figure A-7). […] The ANPR data shows that 45% of vehicle movements 13 in the city are undertaken by older, more polluting vehicles that would not meet the emissions criteria for a charging Clean Air Zone (Table A-5) 14 . Some 24% of fleet movements are undertaken by non-compliant diesel cars, 9% by non-compliant petrol cars, 9% by non-compliant diesel LGVs, and 2% by non-compliant taxis. The remaining 1% of non- compliant vehicle trips relate to petrol LGVs, HGVs and diesel buses. […] In 2019, some 70% of diesel car trips are made by non-compliant vehicles (in 2019). However, by 2022, this proportion is predicted to reduce to 47%, due to natural evolution of the fleet. However, as described above, changes in other vehicle types means that overall contribution of diesel vehicles is actually higher in 2022 than 2018.

It’s interesting to see the results of the automatic number plate recognition study, which says we have a relatively old fleet of vehicles.

the following vehicles are considered non-compliant and are therefore required to pay the charge levied on non-compliant vehicles travelling within the CAZ

Assumption made here without clear justification. There are various ways to setting up a CAZ but this document fails to consider these alternatives.

Over time, it is expected that all roads will achieve statutory NO 2 limit values due to the natural upgrade of the national vehicle fleet to cleaner models.

We have been hearing that for years… we still have illegal levels of pollution.

Charging Clean Air Zones aim to accelerate this turnover and thus need to be maintained only for as long as the statutory NO 2 limit values are exceeded. As soon as it is possible to do so while maintaining legal compliance, these Clean Air Zones can be removed.

Huge unjustified assumption made here! It could be that people switch to public transport and then switch back to cars once the CAZ is removed.

Car ownership in Portsmouth has been growing steadily in recent decades, from 90,200 licensed cars in 2009 to 103,154 licensed cars in 2018, placing additional pressure on the road network and parking provision for residents, visitors and workers.

…caused by Portsmouth City Council and central government failure?

Risk that problem will simply be displaced to other parts of the city (and neighbouring authorities), if inappropriate options are shortlisted. The M275/A3 ‘western corridor’ route is the most attractive route into Portsmouth and there is a risk that any measures to discourage vehicle trips simply free up space for other vehicles to route away from less attractive routes currently being used.

This is a risk particularly for Copnor, Milton and Albert Road. Can this be modelled?

Overall the [public survey] results show that the introduction of even a daily £5 charging point has a marked impact upon non-compliant car travel within and through Portsea Island; 41% would avoid the charging area (changed their destination or not made the journey), 29% would either replace their vehicle or travel using a different mode although 30% would still make the journey in their non-compliant car and just pay the charge.

Around half of the 26 businesses with LGV fleets said they would relocate their business out of the CAZ; and just under half of the 16 businesses with HGV drivers said they would do the same. It is thought that these responses are indicative of the concern businesses in Portsmouth have about a potential CAZ, but that in practice the level of relocation would be much lower.

Interesting survey results here, which underscore the effectiveness of a class D CAZ.

Portsmouth International Port has been excluded from the charging zone due to the potential negative economic impacts.

Lucky them, but is that legal in terms of compliance? How does one get an arbitrary exemption from CAZ?

There are also five road sections on the A27/M27 Strategic Road Network (operated by Highways England) where NO 2 concentrations are forecast to exceed the EU limit in 2022. The highest exceedance is on the section of the A27 immediately north of Portsea Island, requiring a reduction in road NOx of 30% to achieve the EU limit. These are Highways England’s responsibility, but PCC is expected to communicate with Highways England as local plans are developed and ensure local measures do not adversely impact on these sites. […] Under both scenarios there are outstanding exceedances on the Strategic Road Network, but to a lesser extent than in the baseline scenario.

Strategic Road Network exceedances seem to be dismissed since they are Highways England responsibility. Don’t these locations matter? Massive buck passing between government agencies going on. Is this legal?

Finally, a CAZ D (covering all vehicle types) would be most effective, achieving a much greater reduction in road emissions than a CAZ C (29% and 34% on Alfred Road and Commercial Road respectively). This is not surprising as cars (compliant and non-compliant) account for 57% of road emissions on Alfred Road and 61% on Commercial Road (see Figure 2-3). […] Given the forecast proximity of the Alfred Road concentration to the EU limit in a CAZ B scenario, a Level C CAZ applied at a cordon around Portsea Island, as shown in Figure 3-1, is taken forward as the benchmark CAZ against which other options are compared.

CAZ D is highly effective, so why was this not considered as part of the short list? This is a serious omission.

Table 3-5 shows that the Small Area CAZ B performs as well as the Portsea Island CAZ B at exceedance locations on the PCC network. […] While a Portsea Island CAZ B and Small Area CAZ B would both achieve compliance in 2022, a Small Area CAZ achieves a greater reduction in NO 2 concentration and would be implemented more quickly due to the smaller geographical scale. A Small Area CAZ B is therefore shown to deliver compliance in the shortest possible time, without significantly worsening emissions elsewhere, meeting the Primary Critical Success Factor for this element of the Alternative Package. It is also expected to have less of an adverse economic impact on individuals and businesses than the other CAZ B options. A Small Area CAZ B has therefore been taken forward as the basis for the Alternative Package.

The small area CAZ being better seems illogical and counter intuitive. How does the council explain how this could be true? Such a remarkable claim should be discussed in the plan. (Also, a small area CAZ cannot be both the same and better than an entire island CAZ.)

I’m thinking Table 3-4 and Table 3-5 is where the document claims to reach compliance with CAZ. Table 3-8 shows CAZ class B with non-charging additional measures. These are the central claims of the document. These tables show a class B won’t reach compliance, with or without non-charging measures.

From the above quote, PCC are proposing a small area class B CAZ without non-charging measures. That doesn’t meet the critical success criteria of legal compliance (although they say it does). This is literally planning to fail (even with non-charging measures).

There is no table with small area CAZ with non-charging measures, which I imaging will be the council’s first fall back position. We can’t be taking such important decisions based on vague assurances.

Exceedances (>40.49μg/m 3 ) shown in bold […] the concentrations of NO 2 on Alfred Road are very close to the EU limit of 40.49μg/m 3 […] Table 3-8 shows that both packages deliver compliance with the EU limit for NO 2 concentrations in 2022, which is considered the shortest possible time and is a year earlier than predicted through natural fleet upgrades.

In Table 3-5 and others, why is the air quality values being rounded down? That is not legal! The limit is 40.0000 ug/m3 and not any other number the authors invent. Therefore, Table 3-8 doesn’t show “both packages deliver compliance” as full island CAZ B + non-charging is out of compliance! (40.1 ug/m3)

But which approach is faster? The plan talks mostly about 2022. The law doesn’t say choose an approach that has roughly the best compliance timescale, it says to achieve compliance as quickly as possible. No rounding!

Climate change is barely mentioned in the document, which shows a complete lack of joined up, long term thinking. There is no discussion of optimism bias, which is needed “to ensure the Plan meets the requirements of the HM Treasury Green Book methodology”. My previous concerns about the validity of the modelling, etc still remain.

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