1. Air Quality and the DMRB
Mark Chapman, Air Quality and Odour Discipline Manager
mark.chapman@mouchel.com
01483 731378
07976 344 311

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Aim of Today’s Presentation
1. Provide a brief overview of air quality assessment
in the context of Highways Schemes and the
Design Manual for Roads and Bridges.
2. Identify assessment requirements and raise
awareness of when best to engage with Mouchel’s
Air Quality and Odour Team

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Introduction
• Mouchel’s Air Quality & Odour Team
• Setting the Scene – Limit Values and Objectives
• Stages of DMRB Assessment Process
– Scoping
– Simple and Detailed
– Mitigation/Enhancement and Monitoring
• Topics Not Discussed!
• Take Home Messages

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Mouchel’s Air Quality Team
• Operating as a Team for over 4 Years
• Grown to 11 Staff
– One of largest consultancies in UK
• Based in London, Woking and Manchester
• Private and Public Sectors
– Highways
– Industrial
– Odour (Water and Waste Water)
– Dust
– Expert Witness / Public Inquiry

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Mouchel’s Air Quality Team
Highways Agency
• Managed Motorway Schemes
– M60 Manchester
– M3/M4
– M42 Birmingham Box
• HA Subject Matter Expert Forum on Air Quality
• Develop and Test HA Air Quality Assessment
Tools
– DMRB Screening Model v1.5

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Setting the Scene
What Is Air Quality?
• Determined by the presence or absence of
atmospheric pollutants in the air. Poor air quality is
characterised by high concentrations of air
pollution.
Pollutants of Most Concern for Highways Schemes
• Nitrogen Dioxide (NO2) – Human Health
• Particulate Matter (PM10) – Human Health
• Nitrogen Oxides (NOx) – Ecosystems
• Total Carbon (C) – Regional Emissions
– Carbon Dioxide (CO2)

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Setting the Scene
Limit Values, Standards, and Objectives
• CAFE Directive
– Mandatory for Member States
• UK Air Quality Strategy
– Standards and Objectives (Non-Legally
Binding)
• Air Quality (England) Regulations
– Objectives (Legally Binding)

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Setting the Scene
Exposure Periods
• Long-Term
– Annual Mean
• Short-Term
– PM10 – 24 Hour Mean
– NO2 – 1 Hour Mean
Air Quality Management Area
• Where Objectives/Limit Values are not being met
• Local Authorities have a duty to set out actions in
pursuit of achieving the objective/Limit Value
(Air Quality Action Plan)

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Setting the Scene
Highways Agency Policy Objectives
“The Highways Agency will not progress a major
scheme which would worsen the situation overall
regarding compliance with the EU limit value.”
HA Business Plan (2007-08)
“If at any stage of the assessment process, it
becomes apparent that there is likely to be a new
exceedence or a worsening of an existing
exceedence of a mandatory EU Limit Value, then
the Overseeing Organisation must be notified
immediately”
HA 207/07 Air Quality 3/1 para.3.3

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Setting the Scene
Agents involved when notification is required:
1. Air Quality Team
2. Enterprise Mouchel Project Manager
3. Regional Environmental Advisor (Caution)
4. Highways Agency Sponsor
5. Highways NetServe Specialists
6. Air Quality Team

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DMRB Vol. 11, Section 3, Part 1 HA 207/07
• Scoping
– Local Air Quality
• Human Health
• Ecosystems
– Regional Emissions
• Simple
– Local Air Quality
• Human Health
• Ecosystems
– Regional Emissions
• Detailed
– Local Air Quality
• Human Health
• Mitigation/Enhancement and Monitoring
– Local Air Quality
• Human Health

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Scoping Level Assessment
• Seeks to decide which environmental topics are to
be examined in EIAs and EAs and how much
effort should be expended.
• Ongoing activity that is re-activated at key stages
in the project planning process as new information
or available alternatives are narrowed to a
preferred approach to the project.
• Should be carried out for ALL road schemes in
order to determine the level of assessment
required
– Simple
– Detailed

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Scoping Level Assessment
• Determine whether monitoring is required (any
modelling undertaken must be verified using monitored
data).
• Human Health
– Relevant Receptors
• Exposure Periods
– Susceptible Populations
• Elderly, Unwell and the Young
• Ecosystems
– Designated Sites that should be considered are
those for which the designated features are
sensitive to air pollutants, either directly or
indirectly and are one of the following: SACs (SCIs
or cSACs), SPAs, pSPAs, SSSIs, and Ramsar sites.

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Traffic Data Requirements
• Flow
– Annual Average Daily Flow (AADT)
• Speed
– Average Daily Speed (kph)
• HGVs
– Percentage > 3.5 tonnes gross
• Level of detail required dependent on Scheme
purpose, design, location
– Peak Hour
– Congestion Alleviation
– Queuing

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Vehicle Emissions

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Traffic Data Requirements
• Early Engagement
– Input to Traffic Survey Design
• 24 hour 7 Day Count Surveys
• Speed Data
• Vehicle Classification (Manual?)
– Input to Traffic Model Design
• Optimise model setup for minimal data
processing upon receipt

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Simple and/or Detailed Level Assessment
• Simple
– Application of DMRB Screening Method Spreadsheet
v1.03
– Alternative methodology may be required and applied
through agreement with REA/NetServe Specialists
– Inputs
• Traffic Data - Averages
• Background Concentrations
• Detailed
– Application of advanced dispersion modelling (ADMS-
Roads)
– Inputs
• Traffic Data - Profiling
• Background Concentrations
• Meteorological Data
• Monin-Ubukhov Length
• Surface Roughness
• …….. Etc.

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Simple and/or Detailed Level Assessment

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Simple and/or Detailed Level Assessment
• Monitoring
– Annual Mean Objective/Limit Value
– 12 Months
– 9 Months
• LAQM.TG(09) – 75% Data capture ‘acceptable’
– 6 Months – with suitable factoring (subject to
available data)
• 3 Winter Months
• 3 Summer Months
– < 6 Months
• Limited confidence

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Simple and/or Detailed Level Assessment
Model Validation/Verification
• Validation
– Model is fit for purpose, demonstrated by model
developers, HA/CERC
• Verification
– Comparison of model predictions with local
monitoring
– Model adjustment
• Large adjustment factors magnify the positive
and negative effects of a scheme
• Aim to reduce the adjustment required by
improving model setup / input data quality

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Mitigation/Enhancement and Monitoring
• Iterative design, assessment and identification
• Measures that could be taken to
– avoid or reduce adverse impacts; or
– enhance the positive environmental
performance of the Scheme
• In terms of both human health and ecological
impacts

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Topics Not Covered in Presentation
• Economics Appraisals
– Project Appraisal Report (PAR)
– Transport Analysis Guidance (webTAG)
– New Approach to Assessment (NATA)
• Consistent Assessment Approach Required
– Assessment Criteria Different
• Different Study Area
• Different Definitions of Scheme Effects

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Summary – Take Home Messages
• Early Engagement
– Monitoring
– Traffic Modelling Design
• Don’t fear air quality being a ‘problem’
– Plan and Programme
• Talk to us – we can help 

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Contact Details
Mark Chapman
Air Quality and Odour Discipline Manager
mark.chapman@mouchel.com
01483 731 378
07976 344 311
Ana Grossinho
Air Quality and Odour Technical Manager
ana.grossinho@mouchel.com
01483 731 510
07791 643 987