Environmental Engineering Reference
In-Depth Information
3.2 Model Architecture
In order to produce proxy data with standard information (for example, national or
regional census files and business registries), a diagnosis tool was developed in
parallel to the surveys. The tool proposed was defined as a modular model.
Moreover, when possible, the data collection procedure and the modelling
framework were designed jointly in order to maximize the synergies between data
collection (inputs) and data production (outputs). The following chart proposes the
general organisation of the framework. This is an original approach that combines
all the flows related to establishment supply (not only retailing activities but all the
establishments of an urban area), motorized shopping trips and the other B2C
flows, and urban management trips. This approach appears more relevant for
estimating the impacts of urban goods transport on road occupancy appropriately.
Consequently, the result is a significant improvement on existing aids for public
decision-makers regarding urban logistics.
The model is organized in a modular structure, as shown in Fig. 2 . Starting
from standard data (like National Statistics files, census databases and Chamber of
Commerce registries), each module produces results that can be used to feed the
other modules. Consequently, it is possible to estimate the overall impacts of urban
goods transport in an urban area on the basis of only the characteristics of
establishments and those of the urban fabric. This is only possible if the modelling
and simulation unit is the same for each module. If we try to focus on the man-
agement of the urban space to limit congestion and reduce nuisances, the main
question on the transportation of goods in cities is the occupancy of the road
network by delivery vehicles, which compete with the other vehicles (cars, public
transport, soft transport tracks, and pedestrian precincts). The occupancy of the
road network must be considered according to two components which are vehicles
moving and parking for delivery, which explain congestion and conditions of
accessibility.
4 IEM Estimation
The IEM estimation model was presented in Aubert and Routhier ( 1999 ) and
Routhier and Toilier ( 2007 ). However, these papers only presented the mathe-
matical framework, without laying stress on the data collection procedure. In this
section we focus on this point.
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