How should we address model

uncertainty in the assessment of

major infrastructure projects?

Emma Gibbons

2

I don’t have the answer!

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• Model uncertainty in industrial assessments

• Model uncertainty in highways & airport assessments

• Discussion

Outline

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Assessment of model uncertainty in industrial assessments

• Meteorological data

• Buildings

• Terrain

• Coastal effects

• Wind turbines

• Model type

• Background concentrations (all assessments)

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Industrial assessments: meteorological data

• 5 years of met data

• Monitoring station

PC (µg/m3)

at point of

max impact

2011 2012 2013 2014 2015

LT NO2 0.78 0.68 0.75 0.68 0.85

LT PM10 0.06 0.05 0.05 0.05 0.06

1hr NO2 11.4 14.4 12.0 12.6 15.4

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Industrial assessments: buildings

• Buildings

Point of

max impact2015 PC (µg/m3)

Without With

LT NO2 0.46 0.85

LT PM10 0.03 0.06

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Industrial assessments: terrain

• Terrain

Point of

max impact2015 PC (µg/m3)

Without With

LT NO2 0.85 0.94

LT PM10 0.06 0.07

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Industrial assessments: coastal effects

• Coastal effects

No change

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Industrial assessments: wind turbines

• Wind turbines

Point of

max impact2014 PC (µg/m3)

Without With

LT NO2 0.74 0.79

LT PM10 0.23 0.24

1hr NO2 36.9 96.5

24hr PM10 12.7 12.8

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Industrial assessments: model type

• ADMS vs AERMOD

Point of max

impact2015 PC (µg/m3)

ADMS AERMOD

LT NO2 0.94 0.36

LT PM10 0.07 0.03

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All assessments: background concentrations

Sources – Defra, LAQM, PCM, site-specific monitoring

Data – Monitoring station, data availability

• Background concentrations

NO2

PM10

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Assessment of model uncertainty in road assessments

• Traffic data

• Reliability of input data

• Extent of reliability area

• Timing of traffic counts

• Congestion

• Meteorology

• Assessment years

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Assessment of model uncertainty in road assessments

• Urban street-scape

Canyons, traffic lights, bus stops, queuing, tall buildings, car parks.

Canyon Concentration (µg/m3)

Without With

LT NO2 4.9 10.3

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Assessment of model uncertainty in road assessments

• Model verification

Compare predicted and measured pollutant concentrations to validate the air

quality model and adjust where required

• Consideration of uncertainty in air quality trends

Use of tools to take account of future pollutant projections for Highways

England schemes – IAN 170/12

IAQM position statement on vehicle NOx emissions

CURED v2A – AQC tool

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Assessment of model uncertainty in airport assessments

• Traffic data

• Meteorology

• Assessment years – climate change, background concentrations, road transport emissions

What do you think?