Environmental Engineering Reference
In-Depth Information
Therefore a unique optimal speed circulation for atmospheric pollutants for the
whole range of vehicles in an urban vehicles fleet does not exist. Nevertheless, it
is a widely adopted traffic management strategy, because its benefits concern not
only pollutants emissions, but also reduces congestion, noise and traffic accidents.
In addition, the evaluation of air quality management strategies requires the use of
air quality models to perform quantitative impact studies (Ponche and Vinuesa,
2005) and emission data (Baldasano et al., 2008).
This work explores the changes in urban air quality by using the WRF-ARW/
HERMES/CMAQ modelling system, introducing a maximum speed limit to
80 km h
−1
in the access motorways of the Barcelona Metropolitan Area, which is
planned by the regional administration to improve the air quality conditions.
Simulations take into account the entire year 2008.
2. Methods
The Weather Research and Forecasting (WRF) model (Michalakes et al., 2005)
provides the meteorology parameters as inputs to the Models-3 Community
Multiscale Air Quality (CMAQ) model (Byun and Schere, 2006). The High
Elective Resolution Emission Modeling System (HERMES) has been developed
specifically for Spain with a high resolution (1 km
2
− 1 h) (Baldasano et al., 2008).
The traffic emissions module of HERMES considers fundamentally a bottom-up
approach and takes into account 72 diesel and petrol vehicles categories (including
Euro II and Euro III emission standards) according to COPERT III-EEA-EMEP/
CORINAIR methodology; divided by fuel type, vehicle weight, age of the vehicle
and cubic capacity; each of them with its specific emissions factors, defined as a
function of the circulation speed. The emissions account in HERMES traffic module
considers hot exhaust, cold exhaust and evaporative emissions. It also estimates
particulate matter produced by brakes abrasion, tire wear and pavement erosion.
The vehicular fleet is defined for Spain and specifically for Barcelona in this case
of study using data provided by DGT (2004), and distributed in the 72 afore-
mentioned categories. The model includes the definition of the road network,
dividing it in stretches (inside the 1 km
2
cells) with specific temporary disaggregating
profiles (distinguishing day-type: weekday-holiday, and month), specific average
speed, daily average traffic (number of vehicles per day), stretch length, route type
(highway, road or urban) and circulation zones. For the implementation of the
80 km h
−1
limit, data coming from 125 measurement points have been assimilated
within HERMES; these points are located in the access roads to the city of
Barcelona and contain hourly detailed information of average circulation speed
and hourly traffic intensity.
The WRF-ARW/HERMES/CMAQ was applied to the final study area with
domains were defined for the simulations, centering the final domain in Barcelona
