Eval-PDU: urban traffic and its environmental impacts modelling to assess Urban Mobility Master Plan.

Conception of a methodology based on the Nantes’ case

Fouillé L., Broc J.-S., Bourges B., Bougnol J., Schmidt T., Ducroz F., Picaut J. and Mestayer P.

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Introduction

• ANR « Sustainable City » 2008-2012• SEA (Strategic Environmental assessment) method of UMMP

(Urban Mobility Master Plan)

• Application to Nantes UMMP 2000-2010• A chain of models (traffic, emissions, air

quality, noise)• Comparison of real and alternative situations

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1. Needs analysis and problem’s definition

• Toward ecomobility policies and « green » UMMP (since a 1996 act)

• Toward systematic SEA of plans and programs (EU Directive 2001/42/CE)

• Increasing need of tools and methods for ex post and ex ante assessment

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2. Nantes’ case study

• New infrastructures : BHLS (Bus with a High Level of Service,

here the Busway®), P+R (Park and Ride) facilities, tramline extensions, road bridges over the Loire river…

• Many soft actions : mobility management plans, carpooling website, car- and bike-sharing systems, bus lanes…

• Except the Busway (biggest action), the UMMP 2000-2010 seems a program of transition

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3. MethodA. General methodology

Two blocks:1. Core approach : a chain of models2. Peripheral approaches : socioeconomic

consequences (real estate values with a hedonic price model, quality of life and travel behaviour with dedicated social surveys, health impacts with a basic method) and alternative simplified approaches

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B. Description of the chain of the physically-based models

a. Traffic modelling (VISEM/VISUM)b. Atmospheric emissions modelling (CIRCUL’AIR)c. Air pollution dispersion modelling (ADMS

Urban)d. Noise modellinge. Using modelling tools for evaluation purposef. Definition of scenariosa, b, c : existing models are adapted and used.d : a specific simplified model is developed

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a. Traffic modelling (J. Bougnol)

• 4 step Travel Demand Model (TDM)• 11 000 links on the Loire-Atlantique area• Multimodal model : pedestrians, private car,

public transport• Output : Traffic flows for 4 time slots

(distinguishing peak-hours) of a typical working day

Feeding air and noise models

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b. Atmospheric emissions modelling (T. Schmidt et F. Ducroz)

• Based on COPERT IV methodology (emissions levels by average speed and by type of vehicles considering cold start for cars and road gradient for lorries)

• Hourly traffic and average speed• CITEPA vehicle fleet (motorization type, power class, EURO

standard, weight class, number of axles for trucks)• This model also calculates energy consumption• Output : kg per km of 20 pollutant for each link of the

network and each hour of a year• Feeding air pollution dispersion model• Circul’air is a model developed by ASPA (regional air quality

agency Alsace)

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c. Air pollution dispersion modelling (T. Schmidt et F. Ducroz)

• Chemistry/transport model• 3000 road sources (bounded to the Nantes

Metropolis area and simplified network) completed by other ponctual or surface sources (residential and industrial)

• Output : concentrations of pollutants (average, percentile) calculated in various point of an adaptative grid

• A GIS interpolation allows to obtain a complete visualization

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d. Noise modelling (J. Picaut)

• Development of a simplified software using Orbis GIS platform (a GPL GIS)

• Meshing between buildings with a Delaunay triangulation (calculation points)

• Road and/or rail noise• Direct propagation, 1st and 2nd reflexion,

horizontal diffraction• Output: sound pressure level on each point (Ln,

Lden), then interpolated

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e. Using modelling tools for evaluation purpose

• TDM were initially designed for other purposes• The existing literature has proven the feasibility

of using a chain of models (Chiquetto and Mackett, 1995 ; Lee and Jo, 1995 ; Gualtieri and Tartaglia, 1998; Ambrosino and al ., 1999; Brown and Affum, 2002 ; Soleil and al ., 2002 ; Affum and al ., 2003 ; Lagache and al ., 2006 ; Hatzopoulou and Miller, 2010)

• But discussions about scenarios definition and modelling actions remained limited

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f. Definition of scenarios

• 3 reference situations (2002, 2008, 2008 P+R)• 3 integrated scenarios (without Busway,

maximal UMMP, minimal UMMP)• sensitivity tests (individual mobility, fuel price,

public transport prices, public transport frequency, car parking rates, limitations of statutory speeds, evolution of the vehicle fleet...)

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4. Results

traffic (flows and speeds, evening peak hour, focus on the ring road)

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NO2 emissions variation with/without Busway®

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NO2 concentrations variation with/without Busway®

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Variation of the area exposed to a NO2 concentration higher than 40 µg.m-3 with/without Busway®

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Road traffic noise map (including tram lines) expressed in Lden, focus on the town center

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5. Encountered difficulties

• Calibration• Input and output data uncertainties• Presentation/visualization difficulties• Discussion capacity • Experience feedback

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6. Conclusion

• The proposed methodology works• Traffic modelling is a key stage• Some policies are impossible to translate (carpooling or

bicycle promotion...)• Eval-PDU: a tool to visualize and assess transport

policies and their main impacts (traffic, air pollution, noise)

• Complex modelling chain requiring large amount of data and expertise (work remains necessary on simplification and flexibility for decision supporting tool)

Thank you for your attention

laurent.fouille@mines-nantes.fr