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Comprehensive software for modelling road traffic pollution

What is ADMS-Roads?

The ADMS-Roads air pollution model is a comprehensive tool for investigating air pollution problems due to networks of roads that may be in combination with industrial sites, for instance small towns or rural road networks.

Image of City of London NO2 concentration

Vertical cross-section of annual average NO2 concentrations at the site of the Marylebone Road monitoring site in London (shown by diamond). From Hood et al. (2021).

ADMS-Roads combines many of the scientific capabilities of CERC's air quality management system ADMS-Urban with an easy-to-use interface and output pollutant concentrations of very high street-scale (metres) resolution. Model operation is similar to other ADMS models, making it a simple task for anyone familiar with ADMS 6 to extend their modelling skills to cover road sources.

ADMS-Roads Extra

ADMS-Roads Extra is an enhanced version of ADMS-Roads, which typically allows for more sources to be studied simultaneously and buildings effects to be applied to the dispersion from industrial sources. ADMS-Roads Extra essentially works identically to ADMS-Roads, unless stated otherwise in the ADMS-Roads description pages.

For large towns and cities ADMS-Urban is the preferred tool.

Who uses ADMS-Roads?

The ADMS models have been extensively used in local air quality management. ADMS-Urban, on which ADMS-Roads is based, is used across the world for air quality management and assessment studies of complex situations in towns, cities, motorways, counties and large industrial areas.

In the UK, over 70 local authorities have used ADMS-Urban to help with their review and assessment and in developing Clean Air Zones (CAZs), Low Emission Zones(LEZs), air pollution action plans and remedial strategies. The ADMS models have also successfully been used for examining planning applications and EIA for proposed industrial, retail and domestic developments.

ADMS-Roads is currently used by a number of consultancies in the UK and abroad.

Image of NO2 concentrations in M4 and A4 in Hounslow Street view of M4 and A4 in Hounslow

Annual average NO2 concentrations at ground level for study in Hounslow (London) with elevated road (M4, bends to north-west) and ground-level road (A4, continues to south-west).

Image of NO2 concentrations at Bell common Tunnel portal

Comparison of modelled and measured average NO2 concentrations for a 4-week period at the portal of Bell Common Tunnel (M25, London).

Why use ADMS-Roads?

The science of ADMS-Roads is significantly more advanced than that of most other air dispersion models (such as CALINE, ISC and R91) in that it incorporates the latest understanding of the boundary layer structure, and goes beyond the simplistic Pasquill-Gifford stability categories method with explicit calculation of important parameters. The model uses advanced algorithms for the height-dependence of wind speed, turbulence and stability to produce improved predictions.

ADMS-Roads options image

This diagram shows some of the possible inputs to and outputs from the model, and some of the modelling options available. * The buildings module is only available in ADMS-Roads Extra.

Many factors are important in predicting pollutant concentrations. ADMS-Roads has been developed with a number of features to simplify the modelling process and help users. For example:

Visualisation ADMS-Roads has links to ArcGIS and MapInfo Professional GIS (Geographical Information System) packages as well as Surfer contour plotting package. The GIS link can be used to enter and display input data and display output, usually as colour contour plots.
Emissions inventory Source and emissions data can be imported from text files created by the user or exported from CERC's Emissions Inventory Toolkit, EMIT. EMIT contains current and future emission factors including those for vehicles, industrial processes and fuel consumption.
Emission factors Defra's Emission Factor Toolkit emission factors.
Source-oriented gridding ADMS-Roads includes source-oriented gridding option which places extra output points in and adjacent to road sources to give excellent spatial resolution in areas of particular interest.
User-defined outputs The user defines the pollutant, the averaging time (which may be an annual average or a shorter period), any percentiles and exceedence values that are of interest, and whether a rolling average is required. The output options are designed to be flexible to cater for the variety of air quality limits which can vary between countries and over time.

Modelling scenarios and future years

In most cases, ADMS-Roads is first used to model the emissions from a base case scenario, that is, data (emissions, meteorology, background, etc.) are used to produce results that can be verified against locally monitored data from a recent previous year or the current year. Once the base case scenario has been validated, it is possible to investigate different scenarios, for example:

Impact of major development

ADMS-Roads is often used to compare air quality before and after major developments. An emissions inventory is compiled using the best available estimates for after the development. ADMS-Roads allows many What if? scenarios to be tried out, predicting concentrations at key receptors or across a wider area.

Future years

The majority of air quality limits are objectives for future years. These scenarios can be modelled in ADMS-Roads using Defra's Emission factor toolkit emission factors for future years, future predictions from EMIT or the user's own estimate. Likely changes in traffic flows, fleet compositions and background concentrations if known, can also be included in the future scenarios.

Traffic management

If the predictions for future years indicate that concentrations of certain pollutants are likely to exceed the objectives, it is usual to consider traffic management and emission reduction scenarios. For example, some local authorities in the UK have introduced Low Emission Zones within which only vehicles that meet a particular low-emission standard are allowed. The effect on air quality of introducing such measures can be investigated using ADMS-Roads. CERC's Emissions Inventory Toolkit, EMIT can be used for investigating the effect on emissions.

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