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Modelling

Air quality & climate change impacts

King's modelling has provided many air quality estimates in London as part of the city’s planning process, including: assessing the impacts of the Congestion Charging Scheme (CCS), the London Low Emissions Zone (LEZ) and more recently the Mayor’s Air Quality Strategy (MAQS) and Ultra Low Emissions Zone (ULEZ). 

King's have also tested the impacts of large infrastructure such as the Olympics, have improved emissions inventories for those pollutants such as non-exhaust particles, which are poorly understood, and have tested alternative strategies to assess the air quality impacts of climate change policy. Examples of this work include:

The London Low Emission Zone (LEZ)

Numerous emissions scenarios have been tested as part of the development of the LEZ. All of these were run using the London Atmospheric Emissions Inventory (LAEI) and King's emissions and air pollution toolkits. 

During the LEZ impacts assessment phase, scenarios became increasingly complex and included changes in vehicle technologies (split by Euro class) as well as incorporation of particle traps, use of hybrid vehicles, hydrogen fuel cell vehicles and use of selective catalytic reduction.

Olympics impacts modelling

To ensuring road access between central London and the Olympic site, existing traffic was removed or diverted for the period of the games from the Olympic Route Network (ORN). It was important that, as part of the planned changes, no area within London was subject to a worsening of air quality. 

To test this Transport for London’s traffic model was linked to King's London Emission Toolkit (LET) and London Air Quality Toolkit (LAQT) and a highly detailed air quality impacts assessment was undertaken including individual Traffic Regulation Orders (TROs), which applied to specific parts of the ORN. The outputs of the exercise were used to inform potential mitigation measures.

Ultra low emissions zone

Air quality in London remains a problem and this is especially so in central London. The ULEZ project is still ongoing but has sought to eliminate exceedences of the EU limit value for NOby 2020. As part of the ULEZ feasibility study, a number of preliminary strategies have been tested in central London. 


The feasibility work affects all vehicles entering the Congestion Charging Zone (CCZ) with different scenarios being considered for Euro VI vehicles and for zero emissions vehicles, applied during all hours of the year and for charging hours only.
    

Road traffic - PM10 non-exhaust emissions

Using a combination of emissions modelling and ambient measurements, King's have been able to develop road traffic emissions for pollutants which are either poorly understood or for which alternative emissions data is missing. 

In the London Atmospheric Emissions Inventory (LAEI) 2010, non-exhaust road traffic emissions, which were previously based upon methods described in the European emissions inventory guidebook, have been rebased according to roadside measurements described by Harrison et al., 2012. 

The results of this analysis has produced new PM10 tyre wear, PM10 brake wear and PM10 resuspension emissions factors which have significantly increased the non-exhaust emissions within the inventory, as well as reducing the uncertainty of these poorly understood sources. King's is continuing to work on this problem for DEFRA as it is important not only for understanding PM sources and human exposure, but also for projecting to PM air quality in future years. This is because non-exhaust sources are less likely to change over time and will ultimately become the most important road traffic PM10 source.

The impact of alternative air pollution and climate change abatement policies:

Plans to tackle climate change have the potential to provide large health benefits through a reduction in air quality. 

King's, working with colleagues, have published a number Lancet articles describing the effects of a number of alternative air quality strategies including the widespread use of hydrogen for vehicle power (Wilkinson et al, 2007 [s1] ) and also the benefits of adopting conventionally fuelled vehicles which emit the lowest possible levels of CO2 (Woodcock et al, 2009). The health benefits of these strategies have also been compared to other active transport strategies.

The impacts on air quality of plans to tackle climate change is continuing to be investigated at King's for the National Institute for Health Research (NIHR).

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