Accidents and Air Quality Models for EMME/2

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Accidents and Air Quality Models for EMME/2. Marwan AL-Azzawi. Project Goals. Develop series of mathematical models to describe relationship between flows, link attributes, accidents & pollution Allow the user to take account physical characteristics of highways

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### Accidents and Air Quality Models for EMME/2

Marwan AL-Azzawi

Project Goals
• Develop series of mathematical models to describe relationship between flows, link attributes, accidents & pollution
• Allow the user to take account physical characteristics of highways
• Models can be used in any EMME/2 traffic study.
Background
• Accurate estimation of impacts of traffic on accidents and air quality are growing concern to local and central governments.
• Many modern traffic studies also examine impacts of traffic on accidents and pollution, in addition to usual design issues.
• Accident and pollution models are normally estimated as a function of highway type and traffic volumes.
• But in many instances the road geometric layout is omitted.
• This raises a problem with regards to taking into account the different designs and characteristics of different roads.
Data Collection
• Accident Data
• Large data sets input into sophisticated databases
• Measured against different road sections and flow levels
• Multiple regression analysis
• Accident data between 1993 to 1999, for 32 local authorities in Scotland
• Road data has over 30,000 miles of road sections in urban, rural and semi-rural areas
• Total of over 10,000 accident records and 1 billion vehicle miles
• Air Quality Data
• From various test vehicles which measure exhaust emissions from vehicles
• Different travelling speeds to show effects of congestion
• Automatic pollution measuring equipment set up at various locations throughout Scotland (from 1995 to 1999).
• 5 different towns and cities
Types of Accident Models
• Separate models for Fatal, Serious and Slight casualties
• Total is the addition of the model results
• Variables include
• annual traffic flow (million of vehicles)
• width of the road section (metres)
• Length of the road section (metres)
• visibility along the road section (metres)
• surface quality (0 for ‘poor’, 1 for ‘good’)
• if road section is in an urban area (1 for ‘urban’, 0 if ‘non-urban’)
• if road section is in a rural area (1 for ‘rural’, 0 if ‘non-rural’)
• if road section is in a semi-rual area (1 for ‘semi-rural’, 0 if not)
Types of Air Quality Models
• Separate models for the 3 main traffic pollutants Carbon Monoxide (CO), Hydrocarbons (HC) and Nitrogen Dioxide (NO2)
• E = k + aV + bV2 + cV3
• E = emission rate per vehicle (g/km)
• V = vehicle speed (km/h)
• a, b, c and k are co-efficients
• Different co-efficients for different road types
• Relates speed of travel across the link, thereby taking into account the effects of rising and falling congestion levels on the rate at which traffic emissions vary.
Results of Tests
• The models tested against actual measured accident and air pollution data
• Results show new models are statistically satisfactory, with the accident models a little better than the air quality
• This is arguably due to the vast amount of data used to develop the accident database
Future Developments
• Accident Models
• Further disaggregate the models